The Hypro 9910-KIT1990 Pressure Regulator/Control Unit is designed to regulate pressure and liquid distribution control on the Hypro D252 Diaphragm Pump. The Hypro 9910-KIT1990 Regulator comes with one adjustable pressure relief valve, one pressure/bypass selector, a 3/8" hose barb outlet, and a 5/8" hose barb bypass port.