This size 1 filter bag is made of Polypropylene Felt and has a Micron Rating of 25. The Eaton SENTINEL line of bags is fully-welded, is silicone-free, and is designed for easy bag changeouts. Its stable and flexible welded seams adapt to the restrainer basket. The handles in the Polypropylene SENTINEL Ring make replacing the filter quick and easy. Sold in box quantities of 50.