The body reacts to cold and heat by adjusting the blood stream to different parts of the body, like hands, fingers and feet. But the body can not adjust the blood stream to your head. This to ensure the brains function during all conditions. That is why the colder it gets, the more heat you loose from the head by radiation, or even worse, by conduction in the water. You keep warmer with an effective hood. 

VENTED ANATOMICAL HOOD The H1 7mm Hood features a 7mm double layered protection in critical heat loss areas and glideskin seals for the neck andface. Waterproof H1 7mm includes the unique HAVS (Hood AirVenting System) which uses one-way valves to vent annoying air build-up in the hood. 

This diving hood is available as: 

• 5/7 mm H1 Venting Hood 
• 3D Shaped Anatomical Sculpting
• Glideskin Seals 
• HAVS Hood Air Venting System (Double Valves) 
• I-Span Superstretch Nylon 
• Bonded High Quality Nylon Thread 
• Material: Neoprene 
• Reflective Logo 
• Colour: Black. 
• Sizes: S, M, L, XL, XXL