All Cannondale Headshok and Lefty forks use the Headshok size stem which is and has always been 1 9/16″ diameter, just larger than the current 1.5″ standard. There is no compatibility with 1.5″ stems.
When searching for stems on Cannondale Experts, make sure the item title states Headshok and NOT 1.5″.
The shortest stem Cannondale offers is 60mm, the longest up to 140mm from years ago.
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