"Cut and make whatever you want out of it for your custom filtering needs. This sheet of polyester filter fabric is the same as what's used to make our polyester filter bags. These filter bags are made of a micron-rated felt, a non-woven fabric. Small polymer fibers of varying diameters and lengths are forced into a matrix. One side is singed, a process that further locks the filaments together on the ""downstream"" surface. This fabric does not produce an absolute filtration but rather a range based on generally accepted industry tests. Mandy factors influence the actual filtration including the shape, size, consistancy and loading of the contaminates. Also, the feed pressure and rate of flow affects the filtration results. These felts have a far higher dirt capacity and flow rate than a flat woven type bag and is much more resistant to blinding (clogging). The material is meant to be disposable and does not clean as well as a woven material. "