Cobra 3"RPT Slip On Mufflers Chrome 6053 The RPT designation comes from adapting the design from our Race-Pro four-inch muffler into this three-inch size. The bodies begin as three-inches at the front until they expand to three and a half inches at the rear. The tip is also the Race-Pro machined design that's held in place with 12-point bolts. Fits stock headpipes Cannot be sold or shipped to CA