The 3/4" Rubber Repair Kit is compatible with both the 3/4” Model 350 and 350XL Double Check Backflow Preventer. Repair Kit components conveniently include one #1 Check Assembly O-Ring, one #2 Check Assembly O-Ring, one Housing Inlet O-Ring, one Housing Outlet O-Ring, and two Poppets. Repair Kits are sold as accessories for quick and simple repair needs, providing long-lasting protection from backsiphonage and backpressure of polluted water into the water supply.