The Astroman Sun Shirt is our best-selling lightweight stretchy and ultra durable fabric packed with the highest rating of UPF 50 sun protection. Named after the legendary climb in Yosemite Valley the Astroman was built for exposed and rugged climbs but works equally as well for hiking paddling backpacking bushwhacking or any other activity when you're headed out in the blazing sun. bluesign approved 85% nylon 15% spandex Breathable Lightweight Movement-Mirroring Stretch Wicking Quick Drying UPF 50+ Left Welt Chest Snap Pocket Tonal Rubber Snap Front Closure AirVent Inner Back Yoke Shirt Tail Hem