These adapters easily allows the user to switch from megaphones to the stock exhaust system or aftermarket exhaust system that bolts to the original Porsche factory location. The street adapters fit from the header flange to the stock muffler flange. Fits all "European Racing Headers" 911 header systems. Street Adaptors come with all applicable gaskets, nuts, bolts and washers needed. Sold in pairs only. Ask us about Ceramic Coating Services!