The women's REI Co-op lightweight half-zip base layer top wicks and breathes to keep you comfortable hiking or skiing as you go from cold to warm to overheated and back.

• Made of a soft polyester blend that wicks sweat and dries fast to keep you warm in winter and cool in summer
• Spandex in the blend gives the fabric 4-way stretch, while underarm gussets ensure you can reach and move with ease
• High neck coverage with a half-zip front lets you open up for venting when you're working hard
• Flatseam construction is comfortable against your skin
• Lower back hem stays tucked when you stretch
• UPF 50 sun protection
• Fitted