The Cannondale Derailleur Hanger Single Lead F-Si Synapse M12x1 TA ST SS 073 K33049 is the original Cannondale derailleur hanger for 2018 generation Synapse Carbon, F-Si, Topstone Alloy, and Slate bikes. This is an updated version of KP419/ which originally fit Slate, Beast of the East and others. This is the single lead version. Make sure you have the correct axle threads. Double lead (Speed Release) version is a separate version. Call Cannondale with Compatibility Questions.