The Complete Relief Valve Repair Kit is compatible with the 2-1/2”-6” Model 375, 375A, 375AST, 475, and 475V Reduced Pressure Principle Backflow Preventers. Repair Kit components conveniently include one Upper Plunger O-Ring, one Diaphragm, one Seal Ring, one Relief Valve Spring, one Relief Valve Seat O-Ring, and one Relief Valve O-Ring. The accessories within the kit allow you to speed up repairs, while lowering maintenance costs and extending the product life. The Zurn Wilkins portfolio offers long-lasting protection from backsiphonage and backpressure of contaminated water into the potable water supply.