Much of a swimmers body heat is lost through the head while swimming. The Aqua Speed + with Chin Strap is a Polyurethane coated spandex swim cap that provides the comfort of a fabric cap with the thermal properties of a neoprene cap. The Aqua Speed + is not designed to keep water out, but warmth in and is ideal for either pool or open water swimming. Use the Aqua Speed as a base layer under your club or race cap for maximum thermal protection. Chin strap for maximum comfort, does not chafe or restrict breathing Great for open water or pool swimming Polyurethane coated material provides thermal protection Durable & chlorine resistant