This neoprene cap offers extra thermal insulation. Thanks to its 3 mm thick neoprene and thermal lining, it allows you to enjoy swimming in even the coldest waters. Extra Warmth The thermal lining provides added warmth, helping to trap extra heat and avoid heat loss throughout your workout. Comfort The Velcro chin strap allows you to adjust the cap to the shape of your head, providing our most comfortable cap. In addition, the soft thermal lining provides added comfort, preventing chafing which is common with these types of accessories.