REI Co-op Merino 250 Half-Zip Base Layer Top - Women's

Our warmest merino wool base layer top is made with 100% heavyweight 250 g/m² merino wool that naturally wicks away sweat, resists odors and dries quickly. A close-to-body fit keeps it working efficiently, while thumbhole cuffs hold sleeves in place and underarm gussets allow easy movement.

A collar with half-zip neck lets you ventilate as needed, and shoulder seams are rolled forward to help prevent chafing under pack straps. It offers UPF 50+ sun protection and a shirttail hem, plus a locker loop for hanging to dry. Machine wash cold with wool wash product, do not twist or wring, remove promptly; do not bleach; tumble dry low.

Key Features

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

Highlights

• Heavyweight 250 g/m² 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
• Made in a Fair Trade Certified™ factory
• 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

Materials & care

Machine wash cold, use wool wash product, do not twist or wring, remove promptly; do not bleach; tumble dry low

Sizing & fit

Close-to-body fit for optimum performance

How to use

Which material is best?

• Wool: highly moisture-wicking and odor-resistant
• Synthetic: durable and less expensive
• Silk: soft and lightweight for casual activities

Match the temp to the trek

• Lightweight layers: best for moderate to cool temperatures
• Midweight layers: best for cold temperatures
• Heavyweight layers: best for below-freezing temperatures

Find your fit

• Must be close to skin to efficiently wick sweat; should fit comfortably snug
• Base layer is for moisture control; your mid layer is for warmth

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.

Made in a Fair Trade Certified™ factory. 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.

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