How to Choose Base Layers
REI Co-op Lightweight Base Layer Half-Zip Top - Men's
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First half-mile cold; next 3 miles sweaty; lunch break cold. Don't stress—the REI Co-op lightweight half-zip long-sleeve base layer wicks and breathes to keep you comfortable all day.
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- Made of a soft polyester blend that wicks sweat and dries fast to keep you warm in winter and cool in summer
- Spandex in the blend gives the fabric 4-way stretch, while underarm gussets ensure you can reach and move with ease
- Flatseam construction is comfortable against your skin
- Lower back hem stays tucked when you stretch
- UPF 50+ sun protection
- Semi-fitted
- 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 Men's Base Layer Tops| Best Use | Multisport |
|---|---|
| Shirt Type | Partial-zip |
| Fabric | 92% polyester/8% spandex |
| Sun-Protective Fabric | Yes |
| UPF Rating | 50 |
| Moisture Wicking | Yes |
| Quick Drying | Yes |
| Underwear Weight | Lightweight |
| Sleeve Length | Long Sleeve |
| 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.
Buying Advice
More expert advice
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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Most Helpful Favorable Review
Great shirt! Perfect layer in cold locations
Kimberly O2 years ago
Great material! Soft & comfortable. Wood recommend.
Kimberly O
4 people found this review helpful
Most Helpful Critical Review
from a 30 year member
frannyB3 years ago
I’ve been a member of REI for 30 years. In the last couple years I’ve ordered their brand name clothing that turns-out as an embarrassment. I’m so disappointed! I used to get clothing that was made to conventional sizing and constructed to high standards. No more. Today I received a top base layer that was “theoretical “ sized to the same top I bought last year. This one was two inches shorter and an inches narrower than the same item. It’s Cost cutting to the disadvantage of their customers. Very disappointed! This isn’t the first time I’ve experienced this cost cutting but will likely be the last
frannyB
PA
30 people found this review helpful
Customer Images
frannyB
Pennsylvania
from a 30 year member
3 years ago
I’ve been a member of REI for 30 years. In the last couple years I’ve ordered their brand name clothing that turns-out as an embarrassment. I’m so disappointed! I used to get clothing that was made to conventional sizing and constructed to high standards. No more. Today I received a top base layer that was “theoretical “ sized to the same top I bought last year. This one was two inches shorter and an inches narrower than the same item. It’s Cost cutting to the disadvantage of their customers. Very disappointed! This isn’t the first time I’ve experienced this cost cutting but will likely be the last
No, I do not recommend this product
TRIZ
Los Angeles
Good Quality, Low Frills Base Layer
1 year ago
I've, so far, worn this base layer skiing and hiking. It excelled at both. The material is comfortable on the skin and wicks moisture with ease (I even wore it several days in a row without it starting to stink. Don't judge me). The zipper is high quality and, when zipped up fully, didn't do that uncomfortable thing where it presses into the front of your neck. A couple light notes. I wish it had thumbholes. I also wish it was just an inch or two longer for tucking into ski pants without riding up your back on the lift. That being said, an excellent and inexpensive base layer.
Age:35–44
Weight:200–225 lbs.
Height:6'0"
Yes , I recommend this product
bnp9
Pittsburgh, PA
Doesn't seem like it will last
4 years ago
This pullover is exactly what I was looking for. Great weight for outdoor activities without being too warm. However, the first time I washed it per the recommendations, the stitching became unraveled and left a good portion of the bottom seam of the garment undone. Have had similar products from lower tier brands last much longer than 0 wears. Not worth it for this price point. Also bought the midweight half-zip which held up when washed.
Age:25–34
Weight:175–200 lbs.
Height:6'1"
No, I do not recommend this product
Kimberly O
Great shirt! Perfect layer in cold locations
2 years ago
Great material! Soft & comfortable. Wood recommend.
Height:5'7"
Age:25–34
Weight:150–175 lbs.
Yes , I recommend this product
Goose
nh
Form-fitting, stretchy
4 years ago
Medium size weighs 6.5 oz and compresses down to fill just over half of a 1L water bottle. It is see-through material; very thin, yet I imagine it would be rugged enough for hiking or bushwacking. This is a body-hugging style; not quite as tight as biking tights, but still basically form-fitting stretchy material. I returned the item before using it.
Age:65–74
Weight:150–175 lbs.
Height:6'0"
SleepyWeepy
Great running shirt.
2 years ago
I’ve bought many REI base layers over the years, but these are absolutely the best. The body and arm length are ideal and while they appear rather thin in the photos, they are much beefier, a good thing for cold weather running. The material is very comfortable, and I’ve worn this with a thin thermal undershirt in windy cold temperatures down to the low thirties. One of the best REI garments in a while.
Real Reviewer
Greenville
Extremely versatile
1 year ago
It is disappointing REI is discontinuing this item — I have three of them, and they are far and away the most versatile quarter zip I own. Super lightweight with an athletic, non boxy fit over a t-shirt. Both retains and dumps heat when needed. Can wear in the gym, on a run or around town. Can completely beat these up, wash them, wear without washing, etc.
Age:35–44
Weight:175–200 lbs.
Height:5'11"
Yes , I recommend this product
Ethan
Great!
4 years ago
My new go to for base layers. Used to be a capilene guy. Nice work REI!
Yes , I recommend this product
amidetx
Austin, TX
Didn't Breathe Well
4 years ago
Ordered 2 of these Nov 2020. With any activity, got overheated and they seem to didn't breathe. Also accumulated sweat odor quickly and snagged easily. On the plus side, they look like Star Trek uniforms
Age:65–74
Weight:150–175 lbs.
Height:6'2"
No, I do not recommend this product
NH Farmer
Excellent base layer shirt
4 years ago
My husband loves this base layer shirt. I purchased 4 - 2 light & 2 medium weight. He says they are all comfortable and just the right warmth. They wash well; we do not put them in dryer. He is 6 ft, 185 lbs and the Large fits well.
Weight:175–200 lbs.
Yes , I recommend this product
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