Designed to offer protection against damaging UV rays these knee skins perform great in warm conditions, but also offer added protection in cooler conditions. Perfect for days in the mountains of hot exposed climbs and cool descents. Castelli can officially only rate these warmers at UPF 50+, but in their laboratory tests they actually blocked 99.8 percent of damaging UV rays. Using a polyester base they found this it is not only more effective than nylon at blocking UV rays but is also much better at keeping you dry, which means these skins are better in both cooler and warmer conditions. Castelli have kept the construction very clean to eliminate seams that can rub, and used double-sided silicone elastic to make sure they stay in place. They fold up extremely small, so they’re great to stick in your pockets for your next big mountain day. About Leg & Arm Warmers During the Spring and Autumn months, arm, leg and knee warmers are an essential part of a cyclists kit, giving the versatility to cope with unpredictable changes in weather. They are small enough to be carried in a jersey pocket, meaning quick and easy changes can be made while out on the bike. Arm, leg and knee warmers are available in various weights to suit your requirements and the weather conditions you are riding in.