The open, highly aerobic, 3 dimensional structure of Matala Filter Media promotes healthy water conditions and ease of cleaning in a wide variety of filter designs. This is simply the most effective, longest lasting, crush resistant pond filter material available today! You’ll see it featured in every major pond, koi, and fish care magazine. It is a vast improvement over the OEM filter mats standard with most filters/skimmers today & a fantastic upgrade for any brand filter or skimmer! Easily trims to fit any skimmer or filter. Features: A choice of densities allow for step-wise transition from mechanical to biological filtration. Excellent surface area per sq. ft. allows beneficial bacteria to flourish. . High free volume for smooth, even water flow throughout. Very resistant to clogging & easy to clean. Mats are self-supporting, form-stable, rigid and non-brittle. Light weight. Easy to cut to fit with heavy duty scissors, utility knife, circular saw or jig saw! Non-toxic to the environment. Versatile and durable, lasting 6+ years (2-5 times longer than ANY other mat on the market!). OTHER SIZES AND DENSITIES AVAILABLE!