Maytronics Dolphin Spring Cartridge Filter Panel [Qty 4] (9991433 ASSY) lighting The Hayward acrylic machined flow The Hayward acrylic machined flow cell is designed for compatible chemical control and sensing applications where a clear flow cell housing is needed A check valve is useful because it helps keep water moving in the intended direction while reducing the chance of reverse flow through the line A properly selected Maytronics panel set helps preserve original fit and contributes to a more complete filtration refresh and this Maytronics Dolphin version is supplied in a quantity of four using the 9991433 ASSY reference