The H Reversible is identical in design to the TXS RBV-H34 with the exception that the outlet of the valve is a standard Type H female inlet instead of a 34mm hose adapter. This allows the valve to be used either in normal fashion or "reversed". Using the valve in the reversed orientation ensures that the valve will only open up under vacuum. This is perfect for your drag racing car running 35+ psi. This valve requires a vehicle specific mounting flange, sold separately.