REI Co-op Heavyweight Merino Base Layer Half-Zip Top - Women's

View the 19 reviews with an average rating of 4.7 out of 5 stars

$104.95

Get ready for adventures in the cold with our warmest merino wool base layer yet. Made with 100% merino wool, the women's REI Co-op Heavyweight Merino Half-Zip top is supersoft on the skin.

$104.95

$29.83

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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
Collar with half-zip neck lets you ventilate as needed
Thumbhole cuffs hold sleeves in place and help seal warmth in
Underarm gussets are made for ease of movement
Shoulder seams are rolled forward to help prevent chafing under pack straps
Close-to-body fit for optimum performance
Shirttail hem
Weight for size S: 8.8 oz. (250 g)
Locker loop makes it easy to hang this shirt to dry or just keep it off the ground
Machine wash cold, use wool wash product, do not twist or wring, remove promptly; do not bleach; tumble dry low
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 Women's Base Layer Tops

Best Use	Multisport
Shirt Type	Partial-zip
Fabric	100% merino wool
Sun-Protective Fabric	Yes
UPF Rating	50+
Moisture Wicking	Yes
Quick Drying	Yes
Underwear Weight	Heavyweight
Sleeve Length	Long Sleeve
Thumbholes	Yes
Gender	Women's
Sustainability	Fair Trade Certified™ factory From a Climate Label Certified brand

REI Co-op Clothing - Women's

	XXS	XS	S	M	L	XL	1X	2X	3X	0	2	4	6	8	10	12	14	16	18W	20W	22W	24W	26W
Numerical Size	00	0-2	4-6	8-10	12-14	16	18	20-22	24-26	0	2	4	6	8	10	12	14	16	18	20	22	24	26
Bust	31	32-33	34-35	36-37	38.5-40	41-42.5	43-45	47-49	51-53	32	33	34	35	36	37	38.5	40	42.5	45	47	49	51	53
Sleeve Length	29.5	30	30.5	31	31.5	32	32.5	33.5	34.5	30	30	30.5	30.5	31	31	31.5	31.5	32	32.5	33.5	33.5	34.5	34.5
Waist	24.5	25.5-26.5	27.5-28.5	29.5-30.5	32-33.5	34.5-36.5	37.5-39.5	40.5-42.5	44.5-46.5	25.5	26.5	27.5	28.5	29.5	30.5	32	33.5	36	38.5	40.5	42.5	44.5	46.5
Hip	34	35-36	37-38	39-40	41.5-43	44-46	47-49	50-52	54-56	35	36	37	38	39	40	41.5	43	45.5	48	50	52	54	56
Inseam	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31

Sizing Notes

Measurements are stated in inches unless otherwise indicated. Size chart values represent body measurements, not garment measurements. Some women's pants are available in petite and tall sizes. Typically petite sizes fit women 4'11" to 5'3". Regular sizes fit women 5'4" to 5'8". Tall sizes fit women 5'9" to 5'11".

PETITE: Generally, as compared to regular sizes, petite sizes are 2.5 inches shorter in inseam, 1 inch shorter in body length, 1.25 inches shorter in sleeve length and ¾ inch shorter in total rise.

TALL: tall sizes are 3 inches longer in inseam, 2 inches longer in body length, 2.5 inches longer in sleeve length and 1.25 inches longer in total rise.

Capri or cropped pants have an intentionally shorter inseam—reference the technical specs instead of this chart.

Inseam is measured to the floor.

How to Choose Base Layers

What material is best?

Wool is moisture-wicking and odor-resistant, while synthetic fabrics are more durable and less expensive.

Match the temp to the trek

Lightweight layers are best for moderate to cool temperatures. Midweight layers are best for cold temperatures. Heavyweight layers are best for below-freezing temperatures.

Find your fit

To be able to wick sweat efficiently, your next-to-skin layer needs to actually be next to your skin. A comfortably snug fit everywhere is your goal.

More expert advice

What to Wear Hiking

Layering Basics

Close up of someone that has fallen in the snow and is laughing about it.

How to Choose Insulated Outerwear

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.

Ratings Snapshot

Product Rating

4.7

View the reviews with an average rating of 4.7 out of 5 stars19 Reviews

12 out of 12 (100%) reviewers recommend this product

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DebB

Received free product

Woodinville,WA

Rated 5.0 out of 5 stars

7 months ago

This is my new favorite first layer. I’ve been wearing it everyday, that’s how great it is! PROS lightweight Soft Warm Partial zip at neckline CONS The only con for me is that it needs special wash instructions/guidelines - but this is true for all 100% Merino Wool clothing, and it’s worth it for how warm and light the garment is!

Age:45–54

Weight:100–125 lbs.

Height:5'4"

Yes , I recommend this product

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Nice features

Received free product

Salt Lake City UT

Rated 4.0 out of 5 stars

7 months ago

Fabric is great! It's extremely well made. It's a great base layer and keeps me very warm. I'd like to see what other colors this is available in. I received a black one which is not a color I usually wear. It is fitted, which makes sense for a base layer. I usually prefer a little looser fit.

Age:55–64

Weight:150–175 lbs.

Height:5'4"

Helpful?

Sunny Lane Girl

Received free product

Boise, Idaho

Rated 5.0 out of 5 stars

8 months ago

I received this as part of the REI trailblazer program. The one I got is black (you may want to order a different color if you have light colored pet friends at home). The fabric is nice and soft and it feels lighter than I expected. The medium fits great (5'5", 150lb). I love the thumb holes and the sleeves are the right length. I like that the bottom has some curve to the front and back. This top will get a lot of use this coming ski season. I love merino wool. Thanks REI

Age:55–64

Weight:150–175 lbs.

Height:5'5"

Yes , I recommend this product

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Megan H

Received free product

Portland, OR

Rated 5.0 out of 5 stars

7 months ago

This is a functional and affordable option for a merino wool long underwear top. When I first received the shirt it felt slightly itchy. After washing it the itchiness seemed to go away. I wore it for an all day work site visit on a rainy chilly day and it kept me perfectly warm. I like that it has a printed tag at the neck in place of a potentially itchy tag. It is a performance fit without feeling like a sausage casing.

Age:45–54

Weight:200–225 lbs.

Height:5'10"

Yes , I recommend this product

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MamaMB

Received free product

Chattanooga, TN

Rated 5.0 out of 5 stars

7 months ago

I really like this pullover. It’s a great fit for a base layer, and the thumb hole is a nice touch. I like my sleeves to be long enough to cover a bit of my hands with multiple layers and this one worked great. I can’t think of a con! I got black, and the wool feels great. I normally wear a small and I felt it was true to size. It will be a staple for the cooler months—unless my sister steals it from me, she already has her eye on it :) pretty much a perfect base layer!!!

Age:25–34

Weight:125–150 lbs.

Height:5'5"

Yes , I recommend this product

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Lisa

Received free product

Denver, CO

Rated 5.0 out of 5 stars

6 months ago

I love this layer. It’s mid weight but perfect for me—I run a little cooler and appreciate the extra warmth without the bulk. I have worn it hiking and around town under a vest. Have also worn it this weekend under a ski bib. All of the times I have felt comfortable, not too hot. Fit is true to size and meant to be fitted (5’4” 120#, got XS). Washed as directed and it didn’t shrink. Washes up pretty well. I do have to be mindful to wash this separately from my other laundry because I would be really upset if it shrank! Was not itchy at all. I prefer the half zip styles and this zipper was smooth, can be managed with one hand both ways (you know, in case you needed to breathe and didn’t want to take off both mittens). And the thumbholes are always a bonus!

Age:35–44

Weight:100–125 lbs.

Height:5'4"

Yes , I recommend this product

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Sunny Lane girl

Boise Idaho

Rated 5.0 out of 5 stars

8 months ago

I received this as part of the REI trailblazer program. The one I got is black. The fabric is nice and soft and it feels lighter than I expected. The medium fits great (5'5", 150lb). I love the thumb holes and the sleeves are the right length. I like that the bottom has some curve to the front and back. This top will get a lot of use this coming ski season. I love merino wool. Thanks REI

Yes , I recommend this product

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Atl gardener

Received free product

Atlanta, GA

Rated 5.0 out of 5 stars

7 months ago

I love this top. I’ve had similar quarter-zip merino shirts made by other companies, and this one is much softer. I have worn it to work, as a midlayer commuting in cold weather, and trekking. If I could give it more stars I would.

Age:35–44

Weight:125–150 lbs.

Height:5'7"

Yes , I recommend this product

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ORANGEyouglad

Rated 4.0 out of 5 stars

7 months ago

This is a great shirt for someone who looks great in ORANGE, burnt ORANGE. The color is very far from red. I don't live near sequoia trees, if I did I would know "sequoia red" is ORANGE. I wanted a red shirt to wear in the woods so hunters could see me, this ORANGE might as well be camouflage here in SC in the fall. Everything else about this shirt, the weight, the sizing, the neck, the hem is perfect. I don't look good in this color, and it won't help me stand out in the woods. It's ORANGE. If it had been described as fall oak leaf, I would have known it was ORANGE!

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CBinBusan

Rated 2.0 out of 5 stars

5 months ago

I hesitated to buy a S, because i'm on the fence according to the size chart between S and M. But the best color was only in S. I got it. It's HUGE. I mean, it fits me like I imagine an L *should* fit me. And it weirdly buckles in the chest area around the zipper. I had intended this to be something that when I went inside I could strip off other layers and look good, but it fits so weirdly (and is so oversized) that it has to be hidden under others layers. However, it is warm and the color is lovely.

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REI Co-op Heavyweight Merino Base Layer Half-Zip Top - Women's

Features

Technical Specs

Size Chart

Sizing Notes