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  • Lightweight, breathable, pure silk jersey is enhanced with a wicking treatment to help keep you dry and warm
  • Wide, self-fabric elastic waist, seamless sides and rib-knit cuffs provide a comfortable fit throughout
  • Fabric is substantial yet thin enough for everyday wear under jeans or casual pants
  • Machine wash warm on gentle cycle without bleach or fabric softeners, tumble dry low


View all REI Co-op Women's Long Underwear Bottoms

REI membership


Best Use Multisport
Fabric Silk jersey
Moisture Wicking Yes
Quick Drying Yes
Underwear Weight Lightweight
Inseam (in.) 30 inches
Gender Women's

Size chart

Sizing notes

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 and ¾ inch shorter in total rise. TALL: tall sizes are 3 inches longer in inseam and 1 inch longer in total rise.

Rated 5 out of 5 by from Worked great Bought these 2 weeks ago for a 9 day sea kayak trip in Prince William Sound, Alaska. Wore them underneath a pair of fleece pants inside my dry suit. The silk worked really well to keep me warm and dry. They wicked moisture away from my body, and were never clammy or smelly. In the past I used synthetic long underwear and was not happy with it's performance. The silk worked great, I am heading to the store to buy another pair! FYI: For comparison I bought a pair from another company. The REI silk long underwear performance and fit was better. I agree with the other reviewers about buying them a size larger than usual.
Date published: 2014-06-17
Rated 4 out of 5 by from Warm But Fragile These silk undies are a good layer under jeans or other snug-fitting clothing. They are not bulky. I walk a lot and wear mine when the temps dip below 35 for general errand-running. You do, however, have to treat them gently as they snag easily. I wash mine in a lingerie bag on an "easy-care" cycle and hang them to dry. This is my 2nd pair of silk longies in 10 years; if you treat them with care, they will hold up. If they do get a snag, a little nail polish on it stops a run. I also use the matching silk long underwear v-neck shirt and am equally happy with its performance.
Date published: 2011-02-04
Rated 1 out of 5 by from Disappointed I was excited to see the silk long underwear were back in stock and went to get a top and bottom. The top is fine. The material for the bottom is much thinner and looked like it would snag just putting them on. I wear a size 10 and chose the L, but the waistband was so tiny. The size of the legs looked like they would be OK, but I didn't even try them on because I really dislike tight waistbands. Who needs so much elastic for long underwear?? Overall the quality is very disappointing, and they will be going back.
Date published: 2013-11-25
Rated 3 out of 5 by from Not the quality it used to be I have purchased REI silk underwear bottoms over the years. In the past(my last purchase was in 2004,)this product was extremely durable. I found that after 6 years, the elastic waistbands began giving away and that seemed sensible considering the amount of wear and the number or years of wear. I just recently had to purchase new bottoms and after just one day of wear, there were snags and runs in all of the the bottoms. This surprised me as I was wearing the bottoms under fleece, elastic waistband pants, so there were no zippers or rough seams to cause snags. I looked at the 2004 REI silk bottoms that I had purchased and I could not find a single snag or run anywhere. I had worn these bottoms under jeans and slacks, so there was ample opportunity for snags and runs to develop. What has happened to the quality of this product? I would not recommend this product for the price that they are charging for it.
Date published: 2011-01-02
Rated 1 out of 5 by from Not for dirty physical labor... I work outside 40 hours a week doing environmental restoration and trail maintenance. My work provided a white pair, I wore them under Carhartts, but they did not hold up and stayed grossly dirty-looking. They got runs in the knees, and the crotch area completely shredded within a month (Nice to pee in the cold woods maybe!) My 2 other coworkers had the same complaints. I have a pair of REI Midweight Polartec long underwear that I prefer and would actually wear over these when it got really cold in the snow. At least the silkiness felt nice!
Date published: 2011-07-13
Rated 1 out of 5 by from insanely tight elastic waist The waist elastic is waaaaaaaaaaaaaay too tight!!! I'm a size 0 or 2 in jeans or pants and ordered the XS and tried to cut the elastic to make it work with no success. There is no reason for the elastic to be that tight. Wasted money.
Date published: 2011-12-17
Rated 4 out of 5 by from They Shrink - Be Careful! I bought my first set (bottom and top) years ago and loved them. They finally wore out and I bought a new set. The bottoms began tearing at the waist even though I try to be careful when putting them on (hopefully I can mend them as they are expensive). Also, the bottoms and top seemed to feel tighter. I have not had trouble at all with runs. I decided I wanted to have two sets so bought another set yesterday and discovered they are larger than the ones I already have. I measured them and the top's body length and sleeves and the bottom's legs are from 3-3 1/2 inches longer than the ones I already had, meaning they had shrunk that much...and the box says they are "Pre-shrunk for consistent sizing." I am not happy about this but I love the feel of the products when wearing them. I don't want to buy the larger size because they would be too large until they shrank. The box should remove the comment about consistent sizing and warn the buyer that they DO shrink, unless the manufacturer can make good on their word about shrinkage.
Date published: 2011-04-06
Rated 4 out of 5 by from generally comfortable - one fit issue This is my second pair, my first pair pulled out in the crotch and thigh area - even though they looked like they fit fine when I tried them on. So, for the second pair, I bought a larger size that looked too loose in those area - these seams are now holding up fine. Silk knit is fragile - wear it loose, go up a size to avoid stress on the seams. Snags are to be expected with this kind of lightweight knit. I don't mind the snags because they are under-linings. If you don't want this to happen keep your hands smooth and your nails nicely manicured and/or wear cotton gloves while putting them on/off and latex gloves while hand washing them. It's not worth the effort for me. The snug waist elastic doesn't bother me - and I'd rather have it snug because elastic loosens over time. I wear this item daily under casual clothes when the temperature is in the 50's - low 60's. It also makes for comfortable lounge and nightwear. Finally, this item could use a little more fabric in the rear end (crotch length)for those of us with heavily muscled buttocks. In order to get the back end to fit, I had to go up a size and ended up with excess fabric in the front(due to it's longer crotch length) - even then the back waist pulls down a bit. This is often a problem for me. I can take a horizontal tuck in the front to address the excess (crotch length) fabric there - but there is no way to add more to the back crotch length. So the only recommendation I'd have for REI is to add fabric to the back crotch length near the waist - excess fabric can always be easily altered as I mentioned above (in addressing the excess in the front) - but I can't add fabric. Thank-you.
Date published: 2013-12-30
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Is static electricity common when you wear a nylon/spandex-type garment under these? I use them for warming up at the gym, and have tried wearing an UnderArmor thong, but could not get away from it. Suggestions, or just go without the extra underwear?

Asked by: ReannaO
Since the Silk Long Underwear Bottoms are washable, you may want to just try wearing them alone. We have found that drip-drying your delicates prolongs their life-spans as well as reduces the chance of static cling.
Answered by: REIservice
Date published: 2016-12-29
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