2XU Neoprene Swim Cap 2014: For maximum warmth & comfort, swim in the 2XU Neoprene Swim cap. Made from 3mm thick neoprene & featuring a comfortable chin strap this cap is designed to keep you warm whilst swimming open water. When one third of your heat is lost through your head it is a vital piece of equipment for any open water swimmers kit bag. Available in two sizes.