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 are pumping air only on the down-stroke. This is a great option when your inflatable is almost full and there is 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 does not fall off while you are pumping. Volume is 2 liters / stroke. Very effective for topping off large towables in the boat, since peak pressure is an impressive 14 psi.