Activated Carbon Slim Mat, Pack of 3 Consists of activated carbon to absorb the source of yellowing and odors, and a wool mat to catch floating debris. Easy to replace without getting your hands dirty. Replace approximately once every 2 weeks. Compatible with products such as Slim Filter SS, S, M, L, Silent Flow Slim, Glassterior GS, Rakuteria, Rakufill, and AQUA-U.