The best answer is that they are less expensive. Filbur manufactures the same cartridges as the original Hayward, Pentair, Sta-Rite, and Jacuzzi Cartridges using genuine Reemay spunbound polyester media. It's the same cartridge just less money. The End Caps for the Pool and Spa Cartridges are made from a durable polyurethane material. The center cores of the cartridges are comprised of punched PVC pipe for consistent flow.

Click here for more Hayward Pool Filter Cartridge