Here's what other sites are saying:
Whether you're hiking in cold weather, skiing, snowshoeing or mountaineering, the REI Heavyweight Polartec(R) Power Dry(R) Zip-T gives you a warm and moisture-wicking base layer. Polartec Power Dry uses two different yarns on either side of the fabric to enhance comfort; interior yarn wicks moisture and exterior yarn dries quickly. Combination of the two yarns helps keep you dry during highly aerobic activities, moving moisture away from your skin and drying more quickly than single-component fabrics. Center front zipper allows ventilation control; underarm and side gussets promote freedom of motion. Flatseam construction is soft and non-chafing next to skin; offset shoulder seams prevent chafing under backpack straps. Longer length helps the REI Heavyweight Polartec Power Dry Zip-T stay tucked in; smooth texture of outer surface makes it easy to slide on outer layers. Fabric offers a UPF rating of 50+ to help protect against harmful UV light. REI Heavyweight Polartec Power Dry Zip-T features a next-to-skin fit that hugs the body. Closeout.
- REI refers to the men's version