Here's what other sites are saying:
Offering proven value, REI® tall midweight thermal wear is a great base layer for stop-and-go, cold-weather activities like hiking and skiing. High-performance MTS® fabric draws perspiration away from skin to keep you dry and warm. Feels soft against your skin; made of polyester/Lycra® spandex for a stretchy, comfortably snug fit. Four-way stretch jersey knit construction allows unrestricted movement. Functional front fly for convenience. Flat-lock four-needle construction eliminates bulky seams. Easy care: machine wash and dry on cool temperature setting. Fabric provides UPF 50+ sun protection, shielding skin from harmful ultraviolet rays.
- REI refers to the men's version