Patented piston action pumps air in both directions when using High Volume mode. AutoHead automatically adapts to Presta & Schrader valves and solidly locks on with the flip of a lever. Durable anodized aluminum barrel. Rated to 120 p.s.i. and easily fits in a jersey pocket and many seat bags. Two-stage High Volume/High Pressure switch makes high-pressure inflation easy. The Air Handler Mini by Biketube Brand is a powerful and reliable mini pump. At 6.3 inches long, less than 4 oz., it fits in cycling jersey pockets and many bicycle saddle bags. Includes a 2-stage function switch. The HV (High Volume) setting moves maximum amounts of air, and should always be used when beginning to pump a flat tire. The HP (High Pressure) mode should be used for High Pressure tires (above 40 p.s.i.) after pumping in HV mode becomes difficult. When the switch is in HP mode, the pump will move less air per stroke, requiring less force to reach higher pressures. A small amount of air will be released out of the rear of the pump on each stroke. To inflate, push the head firmly on to a Presta or Schrader valve and flip the locking lever up for a secure fit. There is no need to disassemble or thread on. Be sure to support the pump head with the opposing hand while pumping, to avoid damaging the valve. Carefully push the locking lever back down and then pull the pump off the valve. Keep the supplied plug in the pump’s valve hole to keep out contaminants. A second rubber grommet is supplied with the pump, in case the first one ever becomes worn.