Westcoast Saw® 500i/661 Air Cleaner SystemIntroducing a new concept in air cleaner design. This innovative system includes an exterior cage, high density foam, and a polyurethane bushing, which captures dirt and foreign particulates more efficiently than paper or gauze. Whether you're a professional or a heavy duty chainsaw user, this product provides the filtration quality you can rely on. FEATURES: Increased surface area, including breathability from the back side of the filter.