This is a Maytronics Filter and Cartridge Holder for various Dolphin cleaners. This cartridge holder fits the following Dolphin models: Supreme, M4, M5, Liberty, Wave 65, Wave 90, Bio PVC, C3, C4, M400, Triton Plus, Dynamic Oasis, Z5 and Dynamic C3.
Typically two are needed per cleaner, but this item is sold per each.
