Marineland Bonded Foam Sleeve Rite-Size U Filter Media is designed to fit all H.O.T. Magnum Canister Filters. Made with a fine mesh foam, the sleeve traps and holds dirt and debris while its open-cell construction promotes water flow without impairing overall filter performance. The process helps prolong the life of filter media by reducing the accumulation of waste and dirt particles that can prematurely clog a filter. 3 Pack 12 X 24 Inch.