Chung Yang 54mm clutch shoe and 6000rpm spring kit. Now with longer-lasting clutch shoes! Fits Chung Yang CY23RC / CY26RC / CY27RC / CY29RC / GP290 engines. Also fits Zenoah G230RC / G260RC engines. HPI part # 15440. Bolt holes for the 2 mount bolts are 9mm in diameter.