This is a replacement Shimano bottom bracket It is easy to install The oversized axle with eight splines provides a more rigid interface between the crank arm and bottom bracket Key Features Fits Shimano FCM751 FCM571 FCM5108 and FCM4408 cranksets English BSA thread 137x24 Octalink splined drive 73mm shell Axel length of 113mm Weighs 272g

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