These air transfer devices, also called cross-overs, are used to equalize pressure between two dive cylinders. Each unit has a 2-foot, 5,000 psi service hose and a bleeder vent on one end. Both DIN and standard / yoke-mode types are offered. CAUTION: THESE PRODUCTS ARE NOT INTENDED FOR PURE OXYGEN / NITROX SERVICE! SPECIAL MODELS ARE OFFERED FOR THAT PURPOSE.