Shimano Ultegra FC-6503 TANDEM Left Crank Arm OCTALINK 170mm 130 BCD Japan
Bottom bracket interface: Octalink (FC-6503 series). Notes: Classic Ultegra 9-speed triple-era spider with 130/74 mm BCD suitable for outer/middle and inner ring mounting. Model: Ultegra FC-6503 (stamped).