On eBay when you type Cannondale Headshok into the search, you will see multiple results from seller Bikewagon of Headshok linear bearing rebuild kits. There are multiple different ones with different part numbers but the seller is no help in identifying which go with which headshok. The suspension travel on the Silk Road & Silk Tour models is only ~0.75”. I bought a Silk Tour cheap and the Headshok seems to function but honestly the bounce could be more “mush”. The complete bike was $170 I think, but sorry to say I have never ridden it yet. It is in the pipeline with half a dozen other project bikes littering up my basement.