REF BC17647. Retaining ring, exhaust flange. Fits: > 84-25 Big Twin; 86-22 (NU) XL Sportster; 08-12 (NU) XR1200; 87-10 (NU) Buell XB; 07-up S&S X-Wedge engine. Used in combination with OEM style exhaust flanges to install head pipes to cylinder heads.