The Orca Swim Hat is perfect for reducing heat loss from your head so you can stay comfortable in the water with no chin strap. The hat is held in place via a velcro strap at the back of the hat means you can adjust it for the perfect fit without any potential discomfort under the chin MATERIALS100% Neoprene WARMTHMade of 2.5mm neoprene, and with a curved rim design to fully cover the ears, the Swim Hat is perfect for reducing heat loss from your head so you can stay comfortable in the water for longer. ADJUSTABILITY A velcro strap at the back of the hat means you can adjust it for the perfect fit. Please note these hats are a small fit and require a silicone hat to be worn underneath to prevent the hat slipping up.