Pearl Izumi's Thermal Arm Warmers feature P.R.O. Thermal Fleece fabric on the front for warmth and a lighter fabric on the back to vent excess heat. Up top, and on the wrist, the extended cut integrates perfectly with jerseys and gloves to keep cold air out. The specific right and left design provides a superb fit and allows for total freedom of movement. Plus, they boast soft grippers to keep them in place and reflective accents for safety.