How to Choose Base Layers
REI Co-op Heavyweight Merino Base Layer Bottoms - Men's
$99.95
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Get ready for adventures in the cold with our warmest merino base layer bottoms yet. Made with 100% merino wool, the men's REI Co-op Heavyweight Merino base layer bottoms are supersoft on the skin.
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- Heavyweight 250 g merino wool offers a soft feel without the scratchiness
- Made with 100% merino wool that naturally wicks away sweat, resists odors and dries quickly
- UPF 50+ sun protection
- Soft jacquard waistband is comfortable on the skin—and its low profile allows for easy layering
- Crotch gusset is made for ease of movement
- Functional fly
- Close-to-body fit for optimum performance
- Locker loop makes it easy to hang these to dry or just keep them off the ground
- Inseam length: 29 in.; Tall sizes: 32 in.
- Weight for size M: 8.8 oz. (250 g)
- Machine wash cold, use wool wash product, do not twist or wring, remove promptly; do not bleach; tumble dry low
- Made in a Fair Trade Certified™ factory
- 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
Imported.
View all REI Co-op Men's Base Layer Bottoms| Best Use | Multisport |
|---|---|
| Fabric | 100% merino wool |
| Sun-Protective Fabric | Yes |
| UPF Rating | 50+ |
| Moisture Wicking | Yes |
| Quick Drying | Yes |
| Fly Opening | Yes |
| Underwear Weight | Heavyweight |
| Inseam (in.) | 29, 32 inches |
| Gender | Men's |
| Sustainability | Fair Trade Certified™ factory From a Climate Label Certified brand |
REI Co-op Clothing - Men's
| XS | S | M | L | XL | XXL | XXXL | 24 IN Waist | 26 IN Waist | 28 IN Waist | 30 IN Waist | 31 IN Waist | 32 IN Waist | 33 IN Waist | 34 IN Waist | 35 IN Waist | 36 IN Waist | 38 IN Waist | 40 IN Waist | 42 IN Waist | 44 IN Waist | 46 IN Waist | 48 IN Waist | 50 IN Waist | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chest | 35 | 36 - 38 | 39 - 41 | 42 - 45 | 46 - 49 | 50 - 53 | 54 - 57 | |||||||||||||||||
| Sleeve Length | 32 | 32.5 | 33 | 33.5 | 34 | 34.75 | 35.5 | |||||||||||||||||
| Waist | 27.5 | 28 - 30 | 32 - 34 | 36 - 38 | 40 - 42 | 44 - 46 | 48 - 50 | 24 | 26 | 28 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 38 | 40 | 42 | 44 | 46 | 48 | 50 |
| Hip | 33.5 | 34.5 - 36.5 | 37.5 - 39.5 | 41 - 43 | 44 - 46.5 | 47.5 - 50.5 | 51.5 - 54.5 | 32 | 33.5 | 34.5 | 36.5 | 37 | 37.5 | 38.5 | 39.5 | 40.25 | 41 | 43 | 44 | 46.5 | 47.5 | 50.5 | 52.5 | 54.5 |
| Inseam | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 |
Sizing Notes
Measurements are stated in inches unless otherwise indicated. Size chart values represent body measurements, not garment measurements.
SHORT: Some pants are available in short sizes, which generally means an inseam that is 2.5 inches shorter than regular sizes.
TALL: Some pants, shirts, jackets and parkas are available in tall sizes, which generally means an inseam that is 3 inches longer and a rise that is 1 inch longer, a shirt or jacket body that is 2 inches longer, a parka body that is 2.5 inches longer and sleeves that are 2.5 inches longer than regular sizes.
Capri or cropped pants have an intentionally shorter inseam—reference the technical specs instead of this chart.
Inseam is measured to the floor.
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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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JJBARTELL18
Received free product
Minnesota
Comfortable and warm!
9 months ago
I received this product for free from the REI Trailblazers sampling program in exchange for my honest review. I really like the weight of this base layer, but they were a bit baggy, I generally liked a more fitted base layer. I am 6’, 175 lbs and normally wear a size large, so I don’t think the size was off, but maybe a medium might be better. I liked the very soft material, it was not itchy and I really liked the ankle cuffs as they were very sleek and subdued. These were very comfortable and warm.
Age:45–54
Weight:150–175 lbs.
Height:6'0"
Yes , I recommend this product
Loozer
Received free product
Idaho
All the warmth, none of the bulk.
5 months ago
I have gone through a lot of base layers. I use them sking, snow shoeing, and most of all under my dry suit in the winter month while running rivers. I have used these winter hiking and under my drysuit. The hiking is active, and these to a great job of not chaffing and providing breathable warmth. They dont stick to my other layers and they dont sag either. I also like that the ankles stay put, and dont ride up. The flat seams and flat stiching make for a comfortable wear. As far as under a drysuit, they are warm, thin, and provide a little cushion for the hours spent kneeling. I think they are a little tight on the calf, but that could just be me, the guy who doesnt really like the cut of most modern jeans ;). The I would say these are a no brainer if you are thinking about them.
Age:45–54
Weight:225–250 lbs.
Height:6'4"
Yes , I recommend this product
MidAm sportandbikeDad
Received free product
Midwest, USA
High quality, good fit and finish
9 months ago
These bottoms are a great addition to my wardrobe. They fit true to size and are predictably comfortable, as I've come to expect over the last couple of years with REI branded merino gear. They generally stayed put at the ankle/calf but rode up a little when I ended up being stationary and sitting at an early morning soccer game. My only nit-pick: I wouldn't actually characterize these as a heavyweight base layer. I would characterize these as mid-weight. But they do the job I ask of them, adding a layer between my windblown jeans and my skin in the 20s and 30s (F) of low activity outside time or adding a layer for more physical work/exercise at colder temps or with more wind.
Height:6'3"
Weight:175–200 lbs.
KCME
VT and ME
This is not a heavyweight baselayer
7 months ago
I bought the "heavyweight" merino top and bottom for my son for Christmas. He specifically requested heavyweight as he spends considerable time outside in Vermont and Maine, and he gets cold if he's not exercising hard. He has other midweight baselayers so he didn't need more. Well, he got more. This product must be mislabeled. I'm not sure how anyone can call these heavyweight. They are nice quality MIDWEIGHT baselayers. I highly recommend REI change the description.
Midwest Adventurer
Received free product
Chicago, Illinois
Stretchy, Soft Merino Base
9 months ago
I’m 6’0” and 220 lbs, and I got the REI Co-op Heavyweight Merino Base Layer Bottoms in a size medium. The bottoms have an athletic fit but are not restrictive, and the cuffs land just above my ankles. I’ve worn them under pants to several windy, cold soccer practices to watch my kids, and also while trick-or-treating in 40 degree temperatures with gusty winds. These bottoms are smooth, stretchy, and don’t bind under other clothing, making them really comfortable for layering. The merino wool is soft, not itchy, and will be a huge benefit in colder conditions since it retains heat even when damp. The base layer provided the perfect amount of warmth to counteract the cutting wind, and although I haven’t worn them in below-freezing temperatures yet, I’m confident they’ll be an essential layer for snow sports this winter. Overall, these bottoms are high-quality, comfortable, and warm—definitely a great choice!
Age:35–44
Weight:200–225 lbs.
Height:6'0"
Yes , I recommend this product
Triple H
Received free product
Greenville, NC
Good base layer
8 months ago
These base layer pants were good. The fit and is true. They kept me warm on a cool morning run. I want to be able to try them when it get cooler but in the two weeks I’ve had them, the weather has not been very cold.
Age:35–44
Weight:175–200 lbs.
Height:5'10"
Yes , I recommend this product
aaront
Received free product
Baltimore, MD
comfortable base layer
8 months ago
They fit well and are very comfortable. They fit well beneath other pants and I feel like they would keep the cold out, but it's been a warm fall, so I haven't had a chance to try them out in the real world.
Age:45–54
Weight:150–175 lbs.
Height:5'7"
Yes , I recommend this product