This double action pump inflates and deflates towables, kayaks, boats, airbeds, and other inflatables. It delivers a continuous stream of air on both the up and down strokes. Simply turn the release valve counter-clockwise and you're pumping air only on the down-stroke. This is a great option when your inflatable is almost full and there's back pressure. Four universal valve fittings are included to fit Boston valves and stem valves. The accordion-style hose stretches to 5 ft. long and interlocks to the pump, so that it doesn't fall off while you're pumping. Volume is 2 liters / stroke. Very effective for "topping off" large towables in the boat, since peak pressure is an impressive 14 psi.