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  • 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


View all REI Co-op Men's Long Underwear Tops

REI membership


Best Use Multisport
Shirt Style Zip-front
Fabric Merino wool
Moisture Wicking Yes
Quick Drying Yes
Underwear Weight Midweight
Sleeve Length Long Sleeve
Gender Men's

Size chart

Sizing notes

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.

Rated 5 out of 5 by from Impressive warmth in a lightweight package 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.
Date published: 2017-01-11
Rated 5 out of 5 by from Go-to base layer for all my winter activities 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.
Date published: 2017-03-18
Rated 5 out of 5 by from Great base layer shirt I bought this shirt a few weeks ago for work in a cold Fremont Production facility. Often sitting at a desk or moving around doing things I find this shirt keeps in great temperature range. The fit is great and it looks good too, especially in a facility where we wear all black
Date published: 2017-03-09
Rated 5 out of 5 by from Comfortable mid-layer or outer layer Great fit, comfortable and durable material, with no stink! Comfortable indoors or for active wear outdoors during a Montana winter. Great color for hiking, fishing, hunting.
Date published: 2017-01-11
Rated 5 out of 5 by from Great for layering for downhill skiing 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.
Date published: 2017-01-14
Rated 5 out of 5 by from Great wool top 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
Date published: 2016-11-03
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What is the average weight of this garment? I am aware that the gram weight is 200 g/m^2

Asked by: Avocado Cuddler
​The Merino Midweight Half-Zip Base Layer Top weighs 8.5 ounces.
Answered by: REIservice
Date published: 2016-09-09

Is this 100% wool or is it a blend?

Asked by: jasonedean
Our Merino wool base layers are 100% Merino wool.
Answered by: REIservice
Date published: 2016-12-05

Do the sleeves have thumb holes?

Asked by: cliff8406
​This top does not have thumb holes on the sleeves.
Answered by: REIservice
Date published: 2017-01-10
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