This is the Waterproof Drysuit H1 5/7mm Scuba Diving Hood with HAVS Without Bib Features: Durable Nylon 2 Neoprene Rubber Exclusive Hood Air Venting System (HAVS) HAVS System (double vent valves) Valves Eliminate Trapped or Build-Up Air from Regulator's Exhaust 7mm Double Layered Protection in Critical Heat Loss Areas 3-D Shaped Glide-Skin Seal Reflective Logo I-Span Super-Stretch Nylon Glued and Sewn Seams Bonded Hi-Quality Nylon Thread Waterproof's H1 5/7mm nylon-2 neoprene rubber hood with Waterproof's exclusive Hood Air Venting System (HAVS) is constructed with these scientific facts in mind and are proven to keep you warmer when you need it most. That's what Waterproof refers to as facing reality. Waterproof's exclusive HAVS uses double one-way valves to eliminate annoying trapped or build-up air caused by your regulator's exhausted air entering the hood. Hood features a 7mm double layered protection in critical heat loss areas. The hood has an anatomical 3-D shape for a great fit with glide-skin seals, reflective logo, I-Span super-stretch nylon for easy donning. All seams are glued and sewn with bonded hi-quality nylon thread for strength and durability.