How to Choose Base Layers
REI Co-op Merino Midweight Base Layer Half-Zip Top - Men's
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Soft, moisture-wicking 100% merino wool makes the men's REI merino midweight half-zip base layer top an ideal next-to-skin layer for high-performance cold-weather activities.
Shop similar products- Ultrafine 200g merino wool offers a soft feel without the scratchiness
- Merino wool naturally wicks away sweat and resists odors
- Flat seams eliminate chafing
- Tall neck extends coverage; zipper with chin guard lets you adjust ventilation
- Droptail hem stays tucked in and is designed to work under a pack's hipbelt
- Designed to hug the body for optimum performance
- Machine washable
- 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 | Merino wool |
| Moisture Wicking | Yes |
| Quick Drying | Yes |
| Underwear Weight | Midweight |
| 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.
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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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Most Helpful Favorable Review
Impressive warmth in a lightweight package
Ovimo8 years ago
Was concerned for a while about the merino baselayers being itchy, and decided to give it a try, so I was very happy to find out this REI base layer was very well tolerated. Minimal itching and only the first time I wore it.
Otherwise, it is warm and very comfortable. Wore it for skiing and some light hiking. Wicks sweat away pretty effectively, almost as well as my 'plastic' base layers. The zipper is very useful for cooling down also.
You cannot really go wrong with REI products, I have a few and never had any major issues with any.
I'm happy with it.
Ovimo
Texas, United States
15 people found this review helpful
Most Helpful Critical Review
Unsatisfactory Quality
Greg7 years ago
After only the second time I wore the shirt (trail riding) it developed tiny holes in the fabric in the chest area. Both times I had worn it under a mid-weight fleece and nylon shell so it didn't get snagged. I returned it and exchanged it for a SmartWool merino wool half-zip top which has been great. Good return experience with REI - they stand by their products.
Greg
Maryland, United States
7 people found this review helpful
Customer Images
Ruck
Pechanga
Excellent layer
6 years ago
REI got it right with this base layer top. Despite it being just a simple 1/2 zip, midweight merino wool layer, it’s probably the most versatile piece of outdoor clothing I own. It’s comfortable at 70 degrees F, and with just a short sleeve tee shirt underneath, it’s comfortable down to the mid 50’s F. I’ve been comfortable out in the desert down to almost freezing at night, with only a cotton polyester ss tee shirt, this Merino Wool half zip base layer, and a micro-light down vest, no shell. I also like that it’s comfortable, not tight or restricting. I’m a big guy, 6’-1” 240 pounds and the XL fits perfect, plenty long enough for my arms, relaxed cut and stretchy material. Very comfortable. I don’t pack a bag without it now.
Yes , I recommend this product
Zach
Massachusetts
My favorite piece of clothing
4 years ago
I bought this mid-layer on impulse 3 years ago and it has likely been my most used piece of gear since then. I’ve used it climbing on cool fall days and as a base layer while winter hiking many of the four thousand footers in New England. No holes or failures after three years of hard use, just some fierce pit stains. I couldn’t recommend it more.
Age:25–34
Weight:150–175 lbs.
Height:5'6"
Yes , I recommend this product
Ovimo
Texas, United States
Impressive warmth in a lightweight package
8 years ago
Was concerned for a while about the merino baselayers being itchy, and decided to give it a try, so I was very happy to find out this REI base layer was very well tolerated. Minimal itching and only the first time I wore it. Otherwise, it is warm and very comfortable. Wore it for skiing and some light hiking. Wicks sweat away pretty effectively, almost as well as my 'plastic' base layers. The zipper is very useful for cooling down also. You cannot really go wrong with REI products, I have a few and never had any major issues with any. I'm happy with it.
Yes , I recommend this product
Big Dannnnnn
No sweat was obvious to me.
7 years ago
I couldn't feel the sweat on my back until I reached back behind me. There was obvious warmth but not dripping sweat at mile 3 of a 7 mile hike on West Rim at Zion NP.
Yes , I recommend this product
SFSteve
SF, CA
Multi-functional
4 years ago
I sure can't figure out why this garment would be discontinued because it does so many things so well. It's perfect for cool or breezy day hikes, jogs, dog walks, or hanging around the campsite after a long day. Add a light insulation layer and it'll handle some cold. It doesn't pick up or hold odors as synthetics can (and often do). I'm 6', 170, and the medium fits ideally, without bagging anywhere. Personally, I find the texture of the fabric pretty easy to wear, and it works really well at keeping me comfortable in a range of temperatures. When washed, no need to worry about microplastic particles going down the drain. Bought a second after being wowed by the quality of the first.
Height:6'0"
Weight:150–175 lbs.
Yes , I recommend this product
WSHC
Seattle, WA, United States
Go-to base layer for all my winter activities
8 years ago
I've now put this shirt through a full winter season. Wore it under the REI Talusphere insulated rain jacket on long beach walks at Kalaloch (40 degrees and windy), and hiking Smith Rock (29 degrees). Also great base layer for winter cycling, worn under an Ibex "climawool" cycling jacket in Bend, OR, cranking out about 20 miles on gravel with the temperature hovering around 32 degrees. I plan on picking up the non-zippered front option for wearing under button-ups around the office.
Yes , I recommend this product
TomasG
Los Angeles, CA, United States
Great for layering for downhill skiing
8 years ago
I bought this a month ago for use under a Mountain HardWear lightly insulated ski parka. I wore it with either over a short sleeve undershirt or long sleeve thermal undershirt. It was sufficient for temperatures down to 0F, with moderate physical activity. When it gets warmer, it helps to unzip the neck for cooling. The material (merino wool) feels fine against the skin, not itchy.
Yes , I recommend this product
Greg
Maryland, United States
Unsatisfactory Quality
7 years ago
After only the second time I wore the shirt (trail riding) it developed tiny holes in the fabric in the chest area. Both times I had worn it under a mid-weight fleece and nylon shell so it didn't get snagged. I returned it and exchanged it for a SmartWool merino wool half-zip top which has been great. Good return experience with REI - they stand by their products.
No, I do not recommend this product
PaJS
Butler PA
Great wool top
8 years ago
I went in store to buy some smartwool and found these same quality at a slightly lower price no brainer have worn already several times and is great wool piece for price. Smartwool look out
Yes , I recommend this product
Hikingthegorge
Hood River, OR
Great Shirt, poor quality!
7 years ago
I purchased this shirt for use as a base layer hits past winter while I snow shoe. Initially I loved this shirt, it kept me warm, and did a great job. But after 1 month of use, it started to wear oddly where my pack was on my back, and started to develop small holes in the arm, not something I expected from an REI peice, especially at this price, will be returning and getting something else
No, I do not recommend this product
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