Every one of these SNAP-RING bags is manufacturered the same way under ISO 9001 quality standards. That means your filtration results will remain constant year after year. SNAP-RING filter bags by Eaton are manufactured using top-of-the-line materials like the nylon felt used on this bag. This bag is sewn using heavy duty stitching and a stainless steel ring which is used to seal the opening between bag and housing. Part number F31B35563 comes in box quantities of 50. NMO-50-P02S-EH-50 is a size 02, 50 micron bag.