Unicel C7676 Unicel Cartridges are the finest replacement elements you can buy for your pool or spa. The Unicel cartridge material meets or exceeds the original cartridges that the filter for your pool or spa came installed with. The heavy-duty polyester makes the Unicel cartridge capable of lasting longer than cheaper alternatives. Features: -Material: Heavy-duty polyester. -More cartridge pleats mean improved filtering capacity. -Built to the highest possible quality. -Outside diameter: 7. -Length: 29 1/16. -Top inside diameter: 3 with gasket. -Bottom inside diameter: 3 with gasket. -Made in USA.