How to Choose Base Layers

The ultrafine merino wool of the men's REI Co-op Merino 185 long-sleeve half-zip base layer top is an ideal soft, breathable, odor-resistant layer for sweating on the trail—and sleeping in a tent.




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Imported.
View the REI Co-op Merino 185 Product LineView all REI Co-op Men's Base Layer Tops| Best Use | Multisport |
|---|---|
| Shirt Type | Partial-zip |
| Fabric | 100% merino wool |
| Sun-Protective Fabric | Yes |
| UPF Rating | 30 |
| 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 |
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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Great fit and very comfortable. I like the low profile seam stitching. And it comes in tall sizes! I wore this shirt for days and you wouldn’t know it, does the merino thing well and doesn’t stink. Great base layer and even looks good around town. I ordered this and the Smartwool 150. Kept this one and sent the Smartwool back.
REI staff said that the men's MT in wool fit like MT in their synthetic, so I picked one up during Anniversary Sale. At 5-11 and 175# this fit is a little long in the sleeves and torso length...but that is my preference. The fabric is snug and stretchy thru 40" chest and 34" waist. Perfection for a base layer! It will never creep up during reaching or stretching. My 1st foray into wool in the backcountry since the 1980's...durability test pending.
With a 77 inch wingspan the tall size fit perfect. Kept me cool in the heat, warm in the rain and cold. Most importantly kept me odorless on an eight day backpack hunt.
This is my husband’s favorite shirt. He has enough to wear one every day. He is skinny with long arms and the tall medium fits perfectly. We only wish that it came in colors other than black.
I wore this for several days in Yellowstone, doing some 3-11 mile hikes, with temperatures around 35F - 45F. It's a very comfortable, warm but not too warm, versatile base layer. It even did fine keeping me warm on warmer camp evenings (higher 40s.)
Fantastic fit and finish. Merino feels cool to the touch but insulates so we’ll. Perfect sleeve & torso length. Planning to buy a second one. XL Tall
This is unironically the best piece of clothing in my wardrobe. As a tall, skinny guy, it’s hard to find shirts that fit just right, but this quarter zip fits perfectly. Also great for winter hikes, I wear it every time I hike in the White Mountains. I only wish there were more colors so I could buy another.
This is hands-down the best baselayer top I've ever worn. I'm 6'7" and skinny as a rail but the LargeTall fits puuuurrrrrfectly. Which is weird to say because nothing ever fits me that nicely. It holds warmth nicely, but the zip lets you really dump the heat in a hurry if you need to. Looks nice too. I'm so stoked about this product, going to be getting more of them.
Sturdy, warm, comfortable, incredible stitching, great fit, best top ever, only issue is the Tall is not quite super Tall enough for my odd body shape, could use another two inches down the back. Should be fine for most people though.
Fits very well. Particularly being in a tall size. I already have a crew neck long sleeve wool shirt in the tall size and a tall size pair of bottoms. I'm good to go.