Tub/Shower Valve kit Powers 420-451 Upgrade Kit With Bonnet Hydro guard TP e420. This kit is designed to upgrade the 420 Aeration Valve (Part Number XR-0352) to a high flow valve. Kit components include: 1 -Valve Body Assembly, 1 -Piston/Bonnet Assembly, 1 -Piston Seal, 1 -Body Gasket/Crush Washer & 2 each 3 Poly Rubber Packing Bands.