Choose a Cannondale Si BB Adaptor to allow the use of different cranks on your Cannondale bicycle. Cannondale has championed the BB30 bottom bracket “standard” for most of their current frames. However, many riders may want to run something other than the Si style cranks that come as stock equipment on their Cannondale. For this purpose the Cannondale Si BB Adaptor is available to allow the installation of different cranksets into your mountain or road frame. Choose the 73mm to convert a mountain frame or 68mm for road frame use.