Sweat Activated Cooling Technology For riding on hot sunny days, the ultrafris pro's sweat activated cooling technology arm sleeve are essential for staying cool and 100% protected from the harmful UV rays. With elastic silicon grippers, the sleeves will stay in place, are easy to remove and pop into a jersey pocket when not needed. Features: - Sweat and wind activated cooling - UPF 50+ UV protection from harmful rays - Elastic silicon grippers - Breathable fabric - Flatlock seams Nylon 79%, Polyurethan 21%