Browsing for a different look for your bike? This adapter makes it possible to mount an original Harley-Davidson fishtail end cap to your Dr. Jekill & Mr. Hyde | The Exhaust. Because with some bikes the fishtail is an essential part of the look, don’t you think? We offer adapters that fit a Dr. Jekill & Mr. Hyde exhaust and a genuine Harley-Davidson fishtail end cap.