Material: X-Static, Power Mesh Adjustability: elastic back UPF Rating: 30 Recommended Use: summer cycling Manufacturer Warranty: limited Designed to be worn under a helmet, it is thin enough to fit without bunching and light enough to practically disappear when you put it on. You can also expect to stay cool and dry on the ride, thanks to the X-Static Performance Jersey mesh and power mesh side panels on the SPF Ultralight Skullcap.