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.