The SENTINEL line of filter bags by Eaton was designed for bypass-free construction. It features all welded bag seams and a pressure sealing ring that make for an effective and efficient filter bag. NMO-800-P03E-50is a size 03 filter bag that is 800 micron. All SENTINEL filter bags are welded, not sewn. This makes sturdy seams that prevent bypass and eliminate needle holes and loose fibers. This SENTINEL bag comes with a Polypropylene ring. The bag itself is Nylon monofilament. This bag comes 50 per box.