Eaton filter bag PE-1-P01E-WW-50 is a 1 micron polyester bag with polypropylene ring. It is a size 01 bag that comes in boxes of 50. All SENTINEL filter bags are made of silicone-free felt that is welded, not sewn. This makes for a very strong and durable bag that doesn't have gaping needle holes which allow bypass. This is especially important for this 1 micron bag, where a needle hole is much larger than the particles being filtered out. This bag also features a sealing ring and easy access handles for removal.