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. Made to fit size 04 filter housings, Eaton bag NMO-150-P04E-50is a 150 micron filter. 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.