The Pocket Piston is dual action mini pump that fits in your pocket! Half the size of a regular pump yet twice as fast. Dual action pumps air when pushed and pulled. Handy, compact ball pump is around the size of a pen and can fit in your pocket for on the go. Super handy pocket piston is great for bike tires, balls, and small inflatables. Accurately read the pressure for most sports balls. Tandem Sport has been manufacturing and distributing quality volleyball, sports medicine, equipment and training devices to the sporting goods market since 1989.