Aqueon Water Polishing Pads trap fine particles and debris to improve overall water appearance and quality while providing mechanical filtration in Aqueon QuietFlow Canister Filters. Aqueon Filter Media pads are ideal for both fresh and saltwater use. Mechanical filtration pads for Aqueon QuietFlow Canister Filters Traps micro particles and debris Improves overall appearance and water quality Ideal for fresh and saltwater use Small:Fits QuietFlow 200 (#100107312)Large:Fits QuietFlow 300 (#100107313) and QuietFlow 400 (#100107314)