No matter your choice in secondary filtration media, these Mesh Filter Media Bags can handle it. The ultra fine 1/8" mesh on our Fine Mesh Filter Media Bag is ideal for small filter media like carbon or barley pellets while the 1/4" mesh on the Standard and Large Filter Media Bags can handle heavy duty applications of large media types. Each Filter Media Bag is made of long lasting black nylon mesh and utilizes a black draw string and clamp to keep filter media secure.