The Vessel Repair Kit is compatible with the 3/4" Model 350 and 350XL Double Check Backflow Preventers. Repair Kit components include one Pressure Vessel, one #1 Seat, one #2 Seat, one #1 Seat O-Ring, one #2 Seat O-Ring, two Poppets, two Springs, two Sleeves, one Housing Inlet O-Ring, one Housing Outlet O-Ring, four Pressure Vessel Screws, two Test Cocks, and two Test Cock Cap Plugs. Repair Kits are sold as accessories for quick and simple repair needs, providing long-lasting protection from back siphonage and backpressure of polluted water into the water supply.