REI Co-op Merino Thong Underwear - Women's
Avoid panty lines on the trail in the soft, breathable and naturally odor-resistant REI Co-op Merino thong underwear for women. They're made to keep you comfy throughout the day.
- Ultrafine 150 g core-spun nylon, wrapped in merino, offers a soft feel without any itchiness
- Merino wool naturally breathes, wicks away sweat, dries quickly and resists odors, making it an ideal multiday trip companion
- Flat seams and merrow-stitch construction eliminate chafing
- Soft elastic trim keeps underwear in place
- Designed to hug the body for optimum performance
- Machine washable
- Pairs with Merino Bralette and Merino Base Layer Tank Top (not included)
- REI Co-op brand is certified to The Climate Label; we actively fund efforts to reduce carbon emissions across our business and support climate projects around the world
- Made in a Fair Trade Certified™ factory
Imported.
View all REI Co-op Women's Briefs| Best Use | Multisport |
|---|---|
| Underwear Style | Thong |
| Fabric | 48% merino wool/32% TENCEL lyocell/15% nylon/5% LYCRA spandex |
| Moisture Wicking | Yes |
| Quick Drying | Yes |
| Gender | Women's |
| Sustainability | Fair Trade Certified™ factory From a Climate Label Certified brand |
| XXS | XS | S | M | L | XL | 1X | 2X | 3X | 0 | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18W | 20W | 22W | 24W | 26W | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Numerical Size | 00 | 0-2 | 4-6 | 8-10 | 12-14 | 16 | 18 | 20-22 | 24-26 | 0 | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 | 26 |
| Bust | 31 | 32-33 | 34-35 | 36-37 | 38.5-40 | 41-42.5 | 43-45 | 47-49 | 51-53 | 32 | 33 | 34 | 35 | 36 | 37 | 38.5 | 40 | 42.5 | 45 | 47 | 49 | 51 | 53 |
| Sleeve Length | 29.5 | 30 | 30.5 | 31 | 31.5 | 32 | 32.5 | 33.5 | 34.5 | 30 | 30 | 30.5 | 30.5 | 31 | 31 | 31.5 | 31.5 | 32 | 32.5 | 33.5 | 33.5 | 34.5 | 34.5 |
| Waist | 24.5 | 25.5-26.5 | 27.5-28.5 | 29.5-30.5 | 32-33.5 | 34.5-36.5 | 37.5-39.5 | 40.5-42.5 | 44.5-46.5 | 25.5 | 26.5 | 27.5 | 28.5 | 29.5 | 30.5 | 32 | 33.5 | 36 | 38.5 | 40.5 | 42.5 | 44.5 | 46.5 |
| Hip | 34 | 35-36 | 37-38 | 39-40 | 41.5-43 | 44-46 | 47-49 | 50-52 | 54-56 | 35 | 36 | 37 | 38 | 39 | 40 | 41.5 | 43 | 45.5 | 48 | 50 | 52 | 54 | 56 |
| Inseam | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 |
Sizing Notes
Measurements are stated in inches unless otherwise indicated. Size chart values represent body measurements, not garment measurements. Some women's pants are available in petite and tall sizes. Typically petite sizes fit women 4'11" to 5'3". Regular sizes fit women 5'4" to 5'8". Tall sizes fit women 5'9" to 5'11".
PETITE: Generally, as compared to regular sizes, petite sizes are 2.5 inches shorter in inseam, 1 inch shorter in body length, 1.25 inches shorter in sleeve length and Âľ inch shorter in total rise.
TALL: tall sizes are 3 inches longer in inseam, 2 inches longer in body length, 2.5 inches longer in sleeve length and 1.25 inches longer in total rise.
Capri or cropped pants have an intentionally shorter inseam—reference the technical specs instead of this chart.
Inseam is measured to the floor.
Better gear is built together
From feedback to field testing, all of our gear is dialed-in by REI Co-op members. Their adventures informed every stitch and detail—making for better, longer-lasting gear.
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Rei co-op Womens Thong Underwear
These underwear are very soft and comfortable. I hardly noticed I had them on throughout the day! They held up well to washing and drying with no special treatment. I received the size Medium and I am a size 6, 5’5 152 lbs. I wear small Athleta leggings and 6 Lululemon leggings. I would recommend them! If I had one con it would be the waistband gave me a muffintop. But I think that’s more my problem than the underwear ;)
Perfect for running and everything else
I think these are the best merino thong available, with a fair amount of merino content and a flattering cut. I like these better than the Icebreaker Siren—there’s a thicker waistband that’s really comfortable, and a wide enough gusset which I find to be an issue sometimes. It’s soft and not at all itchy; I’m sensitive to wool, so I’d been hesitant to go with merino underwear but I’m glad I did! I bought a pair and kept coming back to buy more, as they quickly became my favorite underwear. Love the colors offered, and that there’s more than just black and beige.
BEST THONG EVER
PLEASE BRING THESE BACK!!! Sweaty butt crack is a thing, these deal with it, and are so comfortable I literally said, "WOW" when I put them on. If I want odor control in clothing, I want it naturally (merino), not from some chemical treatment, especially in my underwear. Just don't make them in baby-diahhrea-green again. Those are hideous. I know on the trail isn't the most likely someone is going to get down and dirty, but I'm pretty sure even a guy would be turned off by a matching bra and panty set in exorcist-vomit-green.
Comfortable, durable, good gusset width.
These are made of comfortable, breathable fabric and a nicely broad elastic waist band that doesn't ride up or down and doesn't roll. Unlike many thongs, its gusset isn't too narrow. As a caveat, I did get a size that verges on too large for me, though, so it might be that the gusset width is due to that. I have had these for a year and worn them while hiking and backpacking, while at the gym, and as swim-bottoms, and they have consistently performed well! Even better, there are very few signs of wear after over a year.
Perfect for adventure activities
I was so worried that I wouldn't like these (because finding good underwear always seems a struggle) but I LOVE these for hiking & backpacking! The merino underwear are super comfortable and breathable, which is perfect for long 10+ mile adventures. The waistband has some stretch to it, but is tight enough to keep the underwear in place so you're not adjusting at all. They're also great for swimming in if you're out hiking to a lake destination and dry off pretty quickly after laying in the sun for a bit. I wish I had bought these sooner for more comfortable outdoor adventures.
Ultimate undies
These are the best undies I've ever worn, they're perfect. Just wore in 90 degrees 75% humidity wetness and they were very moisture wicking and comfy all day. Not sure why thongs are only marketed to women, I pretty much hate boxers and briefs so tried thongs and I'm never going back, total convert. So much more breathable, less material=more comfort. Enough room for all the parts to fit in this style.
Wanted to love these...
I was excited to see REI make a merino underwear. The sizing ran large on me so I exchanged it for a size down. But the waist band was VERY uncomfortable. Its a bare elastic band that didn't stay in place, it rode up around my waist giving me an even bigger wedgie that we don't need in a thong. I decided to try the REI Active Thong and it is PERFECT. I recommend trying these out instead. REI, please fix the waist band in your next design!
Just ok
I wanted to love these so much because I love the matching bralette but the fit just isn't right. The elastic band is too big and not stretchy enough. I'll still wear them because you can't beat the perks of wool underwear for hiking/backpacking but I would recommend the Icebreaker or Smartwool versions over this one unless REI updates it to have a thinner and stretchier top band.
Great for sweaty activities
I've never been a big fan of thongs, but I thought I'd give these a try for running, and they're a game changer. They're so comfortable and they do a great job at preventing chafing. I'm sold!
Comfortable and secure
I really liked this thong more than I thought I would. I was initially put off by how thick the waistband was. I was afraid it would be too tight or constricting. It ended up being a great fit, and instead of being tight, the band felt very secure. I enjoyed the moisture wicking properties of the merino wool. It's one of the reasons I wear wool socks, so I appreciated it in this thong as well. The only thing I would change is that I wish the back were a little thinner, but I did forget about it after is been wearing it for a while. It was a great substitute for my usual underwear, which definitely showed through fitted pants. This thong was invisible under my clothes.