If u a bio wheel filter 150 or 350 any 1 with those cartridges they r costly to keep buying so real easy deal dnt throw away used one remove the blue fiber w a razer empty out old carbon scrap the surface were fiber was attached till get smooth then get some velcro cut lengh And width to fit around the carrtride stick down fill w new media and. Cover w new fiber i use ac carbon fiber ive got three filters going and i havent bought a cartridge in over a year!