Wear the Long Sleeve Baselayer on its own or under your favorite tops to keep your body temp stable. Made from lightweight, 4-way stretch moisture-wicking fabric, YOU-V fabric technology will keep you dry, cool, and protected in the hottest conditions. All YOU-V products feature UPF 50+ protection against the sun's harmful rays. Product Details: Moisture Wicking Breathable UPF 50+ 92% polyester, 8% elastane