Premium Penis Pump Valve Cylinder 2.0in x 12inEach cylinder is hand crafted and made of the finest, industrial strength, crystal clear acrylic The calibrated scale on the side allows you to gauge your size and gains over time. Each cylinder contains a state of the art air valve which allows for quick and easy disconnection from the pump while maintaining pressure within the cylinder. Most men will require the 2 inch diameter cylinder. If your equipment is leaning towards small we recommend the 1.