The Hypro D50 Valve Kit 1920 includes the 4 Valves and the 4 Valve O-rings. If your Hypro Diaphragm Pump cannot draw water or the flow is irregular, one or more of the valves may not be seating properly: if this is the case, Kit1920 may be the solution. Hypro designs their pumps to make the normal wear parts ease to access, thus allowing the operator to change the valves or diaphragms. Instructions for replacing parts are in the Hypro Manual you receive with the pump. Regular pump maintenance ensures a longer pump life.