The De Soto Swim Cap is made from top of the line 3mm GreenGoma 9 limestone derivative rubber so there is no need for a Velcro adjustable chin strap. The thin profile chinstrap maximizes comfort, while minimizing chafing and breathing obstruction. The cap will add more than 5 F (2.8 C) of warmth and water temperature comfort. Until recently, all triathlon wetsuits have been made of petroleum. First in the industry to introduce limestone rubber into wetsuits, De Soto Sport is now incorporating this amazing GreenGoma technology in all of its wetsuits. GreenGoma rubber offers better stretch, buoyancy, durability and insulation with a more closed-cell injected construction thus making it 98.9% water impermeable. So, its lighter, dries quicker and lasts longer while also being a bit more environmentally friendly. All seams are glued.