This design has the Gore Tex membrane bonded around the circumference using a very specialized process. This vent is SELF-VENTING, which means it “breathes” constantly alleviating the need to open and close it. Or in worse case, forgetting to close it! The vent will flow 40 ml/minute max, and SUP’s over 10′ or hollow boards should use two (mid-board & near tail). Originally, Gore designed this vent for sealed military electronics, so it meets very stringent spec’s for a saltwater environment. This vent isn’t an immunity to heat problem with EPS, and customers should understand that boards still cannot be left in the sun; especially upside down on roof racks.