Cal Exotics Optimum Series Master Gauge Penis PumpClearEnjoy a high tech design, impressive suction, and incredible comfort with the Master Gauge Penis Pump. Its built in pressure gauge makes it the premier innovation in pressurized penis pump technology, and its impressive size lets you keep up your pumping routine as you continue to grow to new heights. The penis pump works using a vacuum seal and pressurized suction to increase blood flow to your penis. This creates a harder, firmer erection for you