The KJUS Men's Second Skin Half Zip is a long sleeve base layer for hiking. Soft next to skin and ready to wick moisture away from the skin. Feeling cool? No problem, it'll add a little warmth too. The 1/2 length zipper opens and closes to regulate temperature, so you can adjust on the go. The polyester and spandex blend is nice and stretchy, so movement won't be restricted any step of the way.