Filt-A-Carb Carbon Cartridges are made with top quality activated carbon designed to remove harmful gasses and odors, while clearing up unsightly discoloration.;Undergravel Filter Cartridges are designed to keep your tank looking crystal clear.;Filter Cartridges fit all Undertow and Perfect-a-Flow filters.;Cubes: 0.0005. Weight: 0.1300 lbs.