Any open water swimmer who has experienced water temperatures below 15 degrees will know what Zone3 is talking about when they recommend cold protection for the head. The Heat-Tech neoprene hood not only keeps cold water away from your head, but also warms your body with additional fleece insulation. Of course it does not hinder swimming, but fits perfectly into the overall system. With the Velcro, the chin strap can be individually adjusted. You should wear the Heat-Tech neoprene hood so that the strap fits tightly but at the same time you can still open your mouth completely. Different sizes PLUS the adjustable chin strap make the Heat-Tech neoprene hood a feature you should not miss.