The BILL'S silencer was designed with two things in mind: performance and durability. lighter and sleeker than stock silencers, and is purpose built to perform, as well as give you that classic 2-stroke sound. . 304 stainless steel mid-pipe. Long lasting glass packing. Reinforced mounting brackets. Can be used with either a Bill's pipes or stock head pipe (except where noted). Hand-crafted in the U.S.A.