This rarely used size 04 bag has description: PE-25-P04B-50 and is 25 micron. Whatever the housing, there is an Eaton SNAP-RING bag to fit it. A solid ring (nylon) is sewn into this polyester felt bag to create a sealing surface when the bag is installed. The bag's ability to resist corrosion from chemicals, stand up to solvents and handle high temperatures make it suitable for nearly any industrial process use. Today, tomorrow, a year from now - you know your filter will not change thanks for ISO 9001 quality standards.