The Fastway Spark Arrestor End Cap is designed as an efficient way to convert your stock muffler into a U.S.F.S. approved spark arrested muffler. When the spark arrestor screens are not required, such as at the MX track, simply remove two machine screws on each end cap and take out the screens. Each end cap is machined out of solid 6061 aluminum and anodized with a protective finish. Designed to quickly and easily convert stock, 4-strokes and some 2-strokes, to United States Forest Service (U.S.F.S.) approved mufflers. Machined from solid 6061 billet aluminum for premium durability and finish. Converts a stock muffler into a U.S. Forest Service (U.S.F.S.) approved spark-arrested system - ideal for off-road and trail-legal applications. Designed with removable screens: when spark arrestors aren&&';;t required (for example, on the MX track) the screens can be removed by simply loosening three machine screws on each end cap. Precision engineered, manufactured, and assembled in the U.S.A.