Clear Acrylic Premium Penis Pump Cylinders. Each cylinder is hand crafted and made of the finest, industrial strength crystal clear acrylics. The cylinders are tapered toward the top to match the natural anatomy of your penis for maximum comfort. No gaskets are required. 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 inches diameter cylinder. If your equipment is leaning towards small we recommend the 1.75 diameter cylinder. Likewise, if your above average the 2.25 cylinder would be your choice. Each cylinder measures 9 inches in total length. Cylinders are sold in single units.