Original Cannondale Hollowgram Si single crank arm. Cannondale\'s BB30 innovation many years ago continues today to create some of the lightest, stiffest, strongest, and most versatile cranksets on the market. The Hollowgram Si comes on a variety of mountain and road bikes in the higher price range. This is a significant upgrade from the Cannondale Si solid forged arm in weight savings and stiffness. Interchangeable fit and configuration with Cannondale Si and Hollowgram SiSL2 crank arms. Requires Cannondale SiSL2 style bottom bracket and spindle. Please ask about compatiblity with your bike if you have any questions.Arm Length: 170mmAverage weight: 164g