After 40 hours of research involving interviews with professional athletes, runners, and fabric specialists, plus tests running in 19 °F weather, we think The North Face Winter Warm Tights are the best men’s winter running tights, and the Sugoi MidZero Tight is the best women’s option. Both feature a brushed interior that’s extremely warm and comfortable, and in our warmth and fit tests they bested all competitors. They’re made from stretchy, durable materials that won’t stink up your closet, and they feature enough pocket space for gels, keys, or other personal items.
Our research identified warmth, fit, and specific features like pockets and ankle cuffs as the most important factors in a new pair of men’s winter running tights. Runners we spoke to (including several professionals) also told us that you shouldn’t have to spend more than $100 on a new pair. The North Face Winter Warm Tights met all these criteria and more, as our testers gave this pair the highest scores for warmth, comfort, and fit—by a long shot. Typically it’s a bit pricey, but the dependable nylon/polyester blend, plus the brushed tricot interior, should help ensure that it lasts for several years without stinking up your closet. The design features a single pocket for holding running gels, keys, or credit cards—not a whole lot of space, but certainly sufficient. Unlike with some other winter running garments, we had no trouble finding the Winter Warm Tights at most major outdoor retailers.
For women’s running tights, the calculation was the same: warmth, fit, comfort, and a price tag of less than $100. The clear winner in this category was the Sugoi Women’s MidZero Tight. Our tests gave this pair the edge in warmth (the most important factor), and a narrow second-place showing in fit and comfort (after The North Face Women’s Winter Warm Tights). Ultimately, we preferred the Sugoi pair for its slightly lower price tag (it’s often about $10 cheaper than the Winter Warm); our testers also preferred the style and shape of the Sugoi tights on their legs.
If you don’t want to spend more than $40 on a new pair of men’s running tights, the ASICS Men’s Essentials Tight delivers on warmth, comfort, and fit to an impressive degree, especially considering that this design is intended for year-round use. With a rear zippered storage pocket, this pair can also reliably store gels, keys, or money, making it a viable option for distance runs. In our tests, this pair failed to compete with The North Face Winter Warm Tights, but it proved superior to the rest of the competition in warmth, fit, and comfort.
If you’re a distance runner, or if you’re simply looking for more space to store personal items on runs, we also recommend The North Face Women’s Winter Warm Tights. The design includes two pockets—a zippered front pocket and a smaller key pouch in the rear. Like the men’s version of these tights, this pair is made from a nylon/polyester blend, which delivers the best of both worlds in terms of odor retention, breathability, and long-term reliability. This pair also comes in a few color options, making for a slightly more stylish choice, if you’re into that.
Note: Among the women’s running tights we tested, the only two that our testers found to be sufficiently warm were priced relatively high at the time—between $75 and $85 (Sugoi and The North Face, respectively). For this reason, we didn’t think it was right to make a budget women’s recommendation.
I’ve been an avid runner for about as long as I can remember, having competed in several 5Ks, half-marathons, and track events. I’ve run in just about every environment imaginable, from snowy sidewalks with a 10 °F windchill to July heat waves. More important, I spent dozens of hours interviewing professional athletes, runners, brand representatives, and fabric specialists to get an idea of what makes a good pair of winter running tights, and what people should look for when buying them.
To make any sort of reliable claim about running tights, a reviewer first has to understand what’s out there. We began with some basic Internet research, looking at guides from popular sources such as Runner’s World, Outside, Men’s Journal, The Independent, and Livestrong to see what sorts of tights were available, which ones were the most popular, and why. However, a lot of those guides were out of date, with products that were no longer available or difficult to find, so in making our own picks we tried to keep the focus on tights that were relatively easy to find online. We also looked through customer reviews on retailer sites like those of REI, Dick’s Sporting Goods, Backcountry, and Amazon to get an idea of what people were looking for.
Then we dug a bit deeper. We began compiling a giant spreadsheet of the top-selling, most popular running tights available, including a number of lesser-known items that we thought looked promising. We recorded as many specifications as we could for each style, including the fabric composition, pocket design, sweat-wicking capabilities, waistband type, and price. Then we spoke to the experts, interviewing (by email and phone) six professional athletes, running coaches, and fabric specialists to get an idea of what makes a good, reliable pair of running tights.
Exercise apparel is a surprisingly complicated category; you can find garments for every possible purpose or situation, from yoga pants and fleece headbands to moisture-wicking jerseys and heat-extracting compression sleeves. You’ll also encounter all-weather running tights, which have a variety of uses—from muscle compression to skin protection—but the jury is still out on how beneficial those garments actually are. Winter-weather gear, however, has an obvious value for runners. This guide focuses entirely on running tights designed for cold, outdoor weather. If you do not live in a region where the temperature routinely dips below 50 °F—or whatever threshold you can tolerate without leggings—you really have no reason to invest in a pair.
Making our picks involved poring through a list of more than 60 different pairs of running tights while reading dozens of reviews. I also interviewed, by email and phone, six running experts, athletes, coaches, and fabric specialists. From there we relied on a list of essential features (and a few dealbreakers) to narrow our selection down to 10 running tights (five men’s and five women’s). We used that list to name our initial contenders and our final recommendations, basing our decisions mostly on the advice and experience of the experts we interviewed. Following are the criteria we focused on.
Every expert we spoke to told us that the most important factor in a pair of running tights is the fit, which is a lot more difficult to determine than you might think. While most leggings come in a number of sizes, no two sets of legs are the same. Dylan Bowman, a Red Bull ultrarunner, told us that fit is probably more difficult to dial in on with running tights than with any other type of apparel. “If they’re a little big, it’s uncomfortable and looks silly,” he said, “and if they’re too small you’re probably revealing too much of yourself to your training partners.” Overly tight leggings also restrict movement and inhibit performance.
The problem, from a reviewer’s perspective, is in how to generalize about the particular “fit” of a product when it often comes down to personal details. There will always be physical idiosyncrasies that we simply cannot account for in a comprehensive guide such as this one, so we recommend trying on any pair of leggings before committing to a purchase—even if that means returning them after the fact. Melissa Fehr, a London-based fitness writer, marathon runner, and sewist, told us in an email interview that this can be the difference between slogging through your run and actually enjoying it: “Having kit that you feel great in, that you’re not tugging or pulling, or isn’t falling or twisting as you run, is absolutely key. Because if you’re already suffering and ‘just trying to get through it’ as many novice runners are, one little thing that annoys you about your kit will get magnified until it totally ruins your mood. So having activewear that properly fits you will go a long way towards making running something that becomes a habit, not a chore.”
Other experts, such as trail runner Gina Lucrezi, told us they like to have tights with zippered or elastic ankle cuffs, as such styles help improve breathability and make for an easier experience taking the tights on and off. “Having an easy open access point around your ankles makes putting on and taking off tights much easier, as well as providing a little heat release mid-run by unzipping,” Lucrezi said.
How the tights are cut can also have an impact on fit and comfort. Some tights have bigger waists relative to the hips, some are narrower, and some have tapered leg or ankle openings. The cut affects not only the fit of the tights but also how they appear on your body. In making our picks, we made sure to gather feedback from our testers on how the tights looked and felt on their legs relative to others (how “flattering” they were).
Finally, we gave extra consideration to running tights with waistband drawcords, since they tend to offer a bit more of a customized fit than the elastic alternatives, and they seem to be popular among runners.
Everyone has a different tolerance for cold weather, but it’s safe to say that any pair of winter running tights should be sufficiently warm—that is, capable of keeping your legs warm in climates that dip well below freezing. Features such as fleece- or brushed-back fabrics can add an extra layer of warmth through insulation, as can the composition of the fabric itself. For example, polyester is generally considered to be slightly more breathable than nylon. But how warm you need your leggings to be may also depend on whether you intend to use them as your base layer or your only layer. There’s also the three-quarter-length, or “capri,” style, which is ideal if the weather is too cold for shorts but too warm for ankle-length tights.
We decided to focus on ankle-length tights while giving a slight advantage to those that also came in alternative, capri-style versions. The primary driver for buying a pair of tights is cold weather—this is a point that was stressed by every expert we spoke to, and it covers both winter and all-weather running tights—so it only made sense for us to prioritize the full-length kind. We gave extra features such as brushed interiors and trademarked tech (like Under Armour ColdGear) secondary consideration.
In addition to ankle cuffs and waistband drawcords, we looked for running tights with front or back pockets (preferably zipped). Sweat-wicking capabilities, while pretty much universal in this category, were not the highest priority for us. We did give points for reflectivity, but because this feature is partly a stylistic choice—and because top garments often have more reflective elements—it was not a prerequisite.
Most runners prefer leggings with some sort of pocket, but the mere presence of one or more pockets is not enough; it’s how they’re designed and arranged that really matters. Whether the pockets are for storing energy gels or a house key, they should be effectively positioned so as to prevent chafing, especially if they’re zippered, and they should be readily accessible. We prioritized tights with zippered pockets, though we did not deem them necessary. What was more important for us was making sure the pockets were not merely an afterthought, such as inseam pockets, but that they were actually worked into the design of the tights.
“I’ve seen pockets in some truly bizarre places in RTW (ready to wear) activewear that either wouldn’t even hold a key let alone your phone, or are so far away from the body that they bounce all over,” said Melissa Fehr. “Pockets are necessary, not a feature.”
Most of the experts we spoke to were ambivalent about just how effective or important sweat-wicking tech really is. Most tights have some sort of wicking potential simply by virtue of having a polyester weave, and unless you’re doing half-marathons in the desert, you probably won’t notice the value in it.
That’s not to say you should shy away from sweat-wicking; the ability to draw sweat away from the skin is critical for keeping warm in cold weather, and you’d be hard-pressed to find tights that don’t have this feature. The point is that this is a function that is natural to nylon and, especially, polyester weaves (as opposed to cotton, which is highly absorbent). It’s important to be wary of marketing claims that a certain pair of tights has some unique wicking advantage over any other pair of nylon or polyester tights, because any advantage will probably be to a degree that most people won’t notice—either that, or the claims are flat-out bunk. And besides, any exercise apparel will retain some level of moisture anyway. As Gina Lucrezi told us, “I’m sorry to break the news, but any and every pair of tights will definitely hold some variation of dampness after a run—just a result of working out.”
Melissa Fehr agreed. “Features like wicking material and flatlock seaming tends to be given way more importance by the activewear industry than is actually necessary,” she told us. “I’ve run half marathons in non-wicking leggings with overlocked seams and had zero problems whatsoever.” (Generally, flatlocking refers to seams that are butted together to create a flat, single layer with the thread. Overlocking, on the other hand, refers to a stitch that sews over the edge of one or two pieces of fabric, resulting in a thicker seam.)
To understand how the fabric makeup of a pair of tights can affect warmth, comfort, and performance, you first need to understand the differences between the materials. Some running pants are made from cotton, which is just a bad idea. Cotton is an extremely absorbent material, and in winter climates it can actually be pretty dangerous, as all that built-up moisture has the effect of cooling you down once you’ve stopped exercising. In turn, this can cause hypothermia and have the exact opposite effect from what a pair of running tights should deliver. (The rangers in New York’s Adirondack State Park have a saying: “The best-dressed corpses wear blue jeans.”) Throw in the heightened risk of chafing that cotton poses, and you can see why we decided to nix cotton running tights altogether.
For the most part, though, the category is defined by two main materials—polyester and nylon—and they each have their ups and downs. Polyester is more hydrophobic (water-repellent) than nylon, and so tends to outperform the other in moisture management (aka “sweat-wicking”). However, this is not always the case: As fabric specialist Melissa Fehr explained to us, activewear manufacturers introduce sweat-wicking features by manipulating the weave of the fabric, not the fabric itself. “Unlike a mesh, where water could pass equally well in either direction, the specialist wicking fabrics have a weave which encourages water (sweat) to only go in one direction, away from the body,” she said.
That’s not to suggest that the materials themselves are not important. It’s a fact that nylon is more absorbent than polyester, which means it will likely feel colder when wet, remain wet longer, and, in turn, impede breathability. However, it’s also a fact that nylon is a stronger, more stretchy fabric, which bodes well for long-term durability. But given those dueling characteristics, we decided it made more sense to give polyester the slight edge when narrowing down our list. A blend of the two, though, would certainly be appealing.
Nylon and/or polyester usually constitutes about 80 to 90 percent of the fabric in an average pair of running tights. The rest consists of a stretch material: spandex, elastane, or Lycra, which are all the same thing. What you call the stretch material is not important; what is somewhat important is the ratio of stretch material to the main body fabric (nylon or polyester), as this is the direct measure of a garment’s ability to “snap back” into the same state after you’ve stretched it.
“The more Spandex content, the more stretch and more recovery the fabric will have,” said Fehr. “But if you go too high, you’ll lose any wicking capabilities built into the specialist polyester content. Try working out in some shiny 80’s 100% Spandex fabrics if you don’t know what I mean—they’re insanely hot and sweaty!”
With all these speciality weaves and proprietary sweat-wicking treatments, manufacturers tend to trademark their processes with names like Nike Dri-Fit and Under Armour ColdGear. While some of those details may be important, you shouldn’t let the marketing terminology sway you. The truth is, you can’t really tell a whole lot about warmth or moisture-removal capabilities by the tag alone. You need to try the tights on, test them out, and see how quickly they dry, which is exactly what we did in our tests.
As we waited for test samples of our top picks to come in, we began reaching out to local running groups in the Boston area (where I live). We looked for volunteers who were willing to test out the contenders and provide feedback on what they liked and disliked about each. Over the next few weeks, these volunteers (four women and four men, myself included, all size medium) took time to get runs in with each of the 10 contenders. We asked the testers to score and rank each sample on warmth, comfort, features, fit, design, and value.
From there we were able to apply some hard data to some rather subjective considerations, using average scores to identify the overall favorites. We also tested each pair for its stretchiness, measuring how far we were able to stretch the weave from its resting position; specifically, we pinched the fabric with our thumbs spaced about an inch apart and then pulled to see how much farther we could widen that gap.
If we were looking to purchase a new pair of men’s winter running tights, we would buy The North Face Men’s Winter Warm Tights. This pair was the overwhelming favorite among our testers, ranking high in warmth, comfort, and fit. All of our reviewers agreed it was the warmest of all the tights they tested; it also features a brushed tricot interior that helped it earn far and away the best scores for comfort among all the contenders. Made from a nylon/polyester blend with a 16 percent spandex/elastane weave, it had the most stretchable fabric we tested, able to withstand significant pulling without tearing—a feat that proved challenging for most other tights. The Winter Warm Tights design also includes a single key pocket in the rear, a waistband drawcord, and calf zips (on some models).
In testing all these different garments, we were looking for warmth more than anything else, and the Winter Warm Tights proved to be both warm and comfortable in the harshest of conditions. One tester claimed he ran with these tights in 20 °F weather yet no part of his legs ever felt cold (aside from when he was standing around before and after the run, which is to be expected). On a scale of one to five, our testers gave these tights an average warmth score of 4.5—ranking them significantly higher than any other pair. (The second-highest score was 3.5, shared by the Nike and ASICS tights.)
Our testers also ranked the Winter Warm Tights highly for fit and comfort. On a scale of one to five, they again gave the tights an average score of 4.5; the only other pair that came close was the ASICS Essentials Tight, which earned a score of four. A lot of the comfort factor can be attributed to the brushed, fleece-like interior. The nylon/polyester blend of the main body fabric—a feature absent from every other pair we tested—helps delivers the best of both worlds when it comes to breathability, sweat-wicking, and durability. The result is tight enough to conform to the contours of your legs, but also loose enough for casual wear around the house. One tester said he wore the Winter Warm pair all day and at times even forgot he was wearing running tights.
Another reason why the Winter Warm Tights proved so comfortable: the stretchiness. To measure the pair’s elasticity or flexibility compared with others, we performed a simple test, pinching a section of the main fabric with our thumbs spread about an inch apart and then pulling. The North Face Winter Warm Tights easily tripled the distance between our thumbs—a feat that proved a challenge to every other pair, most of which could hardly double that distance. This could be attributed to the relatively high, 16 percent elastane weave, but the Adidas Men’s Response Long Tights had an even higher spandex thread count (17 percent), and that pair wasn’t very stretchy. More likely, it’s the result of the nylon/polyester blend.
The biggest and most obvious downside to The North Face Winter Warm Tights is the price. Costing $85 at the time of our testing, this is not a cheap piece of exercise apparel; you really have to be an avid winter runner to justify that cost. All of our testers agreed that the price was a bit steep, with one saying he wouldn’t buy the pair if it weren’t on sale. Still, it met our cutoff of less than $100, which all of our running experts agreed was the maximum you should spend on any pair of running tights.
When it comes to features, The North Face Winter Warm Tights offer the bare essentials. You’ll find a rear key pocket (just above the butt) for storing gels, keys, and maybe a small electronic device, but it’s not zippered. The design also provides a waistband drawcord for a more specialized fit, though we found the leggings tight enough for us to ignore this feature. And that’s pretty much it—no reflectivity, no internal or side hand pockets. The North Face claims on its website that the Winter Warm Tights come with calf zips, but the sample we acquired did not have any zips or openings at the ankle, making the leggings just a tad difficult to remove.
If we were looking for a pair of tights that would keep our legs warm on long runs, but we didn’t want to spend more than $40, we would buy the ASICS Men’s Essentials Tight. This pair was the clear runner-up among our testers, scoring high in warmth, comfort, and fit (but still coming in second to the Winter Warm Tights in all those respects). While this pair is still rather sparse on features and hardly as warm as our main pick, it is an excellent budget option for year-round running.
Along with the Nike Track Running Pants, the Essentials Tight scored an average of 3.5 (out of five) for warmth—not great, but second only to the Winter Warm Tights. The weave is mostly polyester (92 percent), with an 8 percent spandex count; this combo makes for a highly effective sweat-wicking potential in a semi-compressive body. One of our testers said this pair was uniformly tight, which you could see as good or bad depending on your size preference. In all, our testers gave the Essentials Tight an average comfort score of four. (Only The North Face Winter Warm Tights scored better in this regard.) These tights are also pretty stretchy: In our stretch test we were able to double the distance between our thumbs—a measure that was more or less comparable to that of every other contender (aside from the Nike pair, which was less stretchy, and the North Face pairs, which were the most stretchy).
Like The North Face Winter Warm Tights, the ASICS pair is somewhat sparse in the features department, offering a waistband drawcord and a single back zipper pocket for storing gels, keys, and small electronics, but nothing else. It meets our minimum requirements, but in no way exceeds them.
While we think these tights will be plenty warm for most circumstances, the real appeal is in how they balance comfort, fit, and affordability. ASICS even promotes them as more of an all-season pair of running tights. Dara Reitner, a public relations manager at ASICS, specifically told us, “The Essential Tight is considered a year-round, entry-level price point tight… perfect for transitional times of year, but maybe not dead of winter.”
Even so, one of our testers said the Essentials Tight was outright “toasty,” while another, more budget-conscious tester said it was the only one of the contenders he would ever actually buy.
If we were going to buy a new pair of women’s running tights for use in cold weather, we would buy the Sugoi Women’s MidZero Tight. This pair had the highest average score among our testers, earning big points for comfort, design, value, and especially warmth—all of the testers agreed it was the warmest of the contenders they wore. With a soft brushed interior, the Sugoi MidZero Tight is likely to be more comfortable than most competitors of its kind. The only other tights that might compete in this regard are The North Face Women’s Winter Warm Tights, which also feature a brushed, fleece-like interior and an equally warm fabric blend. While both scored well on warmth and comfort, the Sugoi pair’s slightly higher warmth rating, as well as its somewhat cheaper price tag and more flattering design and fit, convinced us that it is the better women’s option for most people.
When it comes to winter running tights, warmth is the most important factor, and the Sugoi MidZero Tight proved to be the warmest of all the women’s tights we tested. Measuring for warmth on a scale of one to five, our testers gave this pair an average score of four. The only other pair that came close was The North Face Women’s Winter Warm Tights, which got an average warmth rating of 3.75. One of our testers ran with the Sugoi tights in 19 °F weather and reported that her hips and behind were a bit cold, but on the whole she was “very happy with the warmth level, considering how cold and windy it was.” Another tester stated bluntly that this pair was the “warmest of the bunch,” while a third said her “legs were warm from the beginning to the end of the run.”
The Sugoi Women’s MidZero Tight also scored well on comfort and fit. Despite the high warmth rating, none of our testers ever felt overheated, and they all gave the Sugoi pair solid scores for comfort, breathability, and fit. On a scale of one to five, the tights received an average comfort rating of 4.25; The North Face Winter Warm Tights beat that with a score of 4.5, but we felt this difference was negligible when we considered it in context of everything else, particularly the price. (The Winter Warm Tights cost $10 more at this writing.) One tester said she wore the Sugoi pair around her office for a few hours and thought it was “very breathable.” This is probably due to the relatively high polyester thread count (88 percent, with 12 percent spandex), as that material is principally responsible for sweat-wicking and “breathing” functions.
Most testers also agreed that the Sugoi pair had a superior design, despite its simple black exterior. When our testers evaluated aspects such as the style, seam location, waistline, and overall appearance, they gave the Sugoi MidZero Tight an average score of 4.25—a higher mark than for any other contender. Two testers independently commended these tights for their “flattering” seam line and locations. More bluntly, one tester said, “These look good, fit well, and kept me warm.”
Like its chief competitor (The North Face Women’s Winter Warm Tights), the Sugoi MidZero Tight doesn’t offer much in the way of features. The single internal pocket is large enough to fit a set of keys, some credit cards, or a running gel. The pair has a waistband drawcord, but most of our testers agreed the leggings were tight enough that it wasn’t necessary. The ankle cuffs feature a rubber band that’s supposed to grip the leg and prevent the tights from riding up, but for our testers it mostly served as a point of confusion—one tester thought the rubber was outright uncomfortable, and another thought it made for a looser cuff. Still, this wasn’t enough to constitute a dealbreaker, as both of those testers still agreed on the MidZero Tight as their favorite of the bunch.
Also like The North Face Winter Warm Tights, the Sugoi pair typically has a fairly hefty price tag, which may discourage some shoppers. At $75 at this writing, it’s a steep investment; one of our testers (who admitted that she is not an avid runner) said she’d never pay that much. This pair does feel rugged and durable enough to be a worthy investment, one that should last for several years—although we cannot say for certain that it will.
If you can’t find the Sugoi Women’s MidZero Tight, or if you’re looking for something with more color options, more secured pockets, or a less intrusive ankle cuff, we recommend The North Face Women’s Winter Warm Tights. This pair costs a bit more but scored nearly as well as the Sugoi pair in warmth, design, and value, and even exceeded it in features and overall comfort.
The Women’s Winter Warm Tights are fairly similar to the men’s version. Made from a blend of 55 percent nylon, 29 percent polyester, and 16 percent elastane, and featuring a brushed tricot interior, this particularly warm pair is also both comfortable and breathable. Measuring for warmth on a scale of one to five, our testers gave the Women’s Winter Warm Tights an average score of 3.75, just 0.25 less than the main women’s pick. This pair also exceeded the Sugoi Women’s MidZero Tight in comfort, with a score of 4.5. Testers agreed that this pair stayed relatively dry and clean even after a sweaty run, and that the tights were easy to slide in and out of. The fit was tight but not compressive, and most testers said it produced a flattering seam line, although not quite as much as the Sugoi pair.
Unlike the men’s version, the women’s pair has two pockets—a zippered one in the front and a key pouch in the back. This design marks a substantial break from other tights in the category, providing a solid option for long-distance runners who require space to store gels, cash, keys, or credit cards—although the volume of storage is still far from what anyone would consider “spacious.” The tights also have a waistband drawcord, and (depending on the store) you can find the pair in several colors, including deep garnet red, darkest spruce, and asphalt grey.
Adidas Men’s Response Long Tights: We saw some decent customer reviews of this pair for general-purpose running, but our testers found it to be too tight, too pricey, and not nearly warm enough.
Nike OTC65 Track Men’s Running Pants: This design offers some convenient features, including zippered side pockets and ankle cuffs. The pair also proved moderately warm (though not nearly as warm as the Winter Warm Tights) in our tests. In the end, however, none of those perks justify the hefty price tag.
Saucony Men’s Boston Pant: The zippered pockets were about the only thing going for these pants, which suffered the lowest average scores from our testers.
Champion Women’s 6.2 Performance Workout Legging: This pair was especially inexpensive and scored well for its unique design. It was not very warm, however, and all the testers said it didn’t fit well.
New Balance Women’s Accelerate Tights: After our two main women’s picks, this New Balance pair enjoyed the highest ratings for warmth, but its scores were still low enough to discourage us from recommending it. Overall, our testers were turned off by the fit and the rather high price tag.
Champion Women’s Absolute Workout Legging: Affordable and well-designed, this Champion pair may be a decent pick for casual wear—maybe for yoga or warm-weather exercise. For running in cold weather? Not so much.
(Photos by Michael Hession.)
That dinner was delicious.