Pentair Piston Assembly [Slide Valve, Push-Pull Kit] (263055) pleatco and this Filbur FC-9860 grid

and this Filbur FC-9860 grid is designed in an 18 inch by 20-3/4 inch format for matching pool applications

or damaged enough to reduce effective flow and debris capture

or no longer fits the housing the way it should

Helps capture leaves and larger debris at the skimmer

and PBH50 references

Pentair Piston Assembly [Slide Valve, Push-Pull Kit] (263055) pleatco and this Filbur FC-9860 gridThis piston assembly is built for compatible Pentair slide valve and push pull valve service. Push pull valves rely on a smooth moving piston to shift flow between filter and backwash functions, and wear in this area can lead to leaks, hard operation, poor sealing, or incomplete valve movement. Replacing the piston assembly helps restore controlled valve action without replacing the full valve body. It is useful during backwash valve rebuilds,