The Aquascape medium density rigid filter Mat provides efficient mechanical and biological filtration for your pond. The filter Mat measures 24 by 39 and can be easily cut to your desired size and shape using a serrated knife. This allows for installation in a wide variety of Skimmer boxes and filters. Aquascape medium density rigid filter mats are 1.5 thick and extremely easy to maintain, only needing to be cleaned periodically. For best results we recommend combining different densities to maximize mechanical and biological filtration - Aquascape offers three (3) Mat densities: low, medium and high. For over 25 years Aquascape has been the leading innovator in the pond industry, creating unique and Proven products to enhance the water gardening experience.