This is a polyester felt filter bag made by Eaton. Called a SENTINEL bag, this filter features a polypropylene ring with a pressure activated seal. Bag PE-50-P02E-WW-30 is 50 micron, size 02, and comes in box quantities of 30. All SENTINEL bags are silicone-free and are welded, not sewn. Designed to be bypass-free, this bag is up to handling some serious industrial jobs. Aside from being physically strong, the plastics used are highly chemical resistant, making it a good choice for a range of media.