This aero seat collar is what comes standard on the Cervélo Soloist Carbon and Soloist Team framesets. It is also compatible with the Cervélo SLC-SL. It'll come in handy if you find a way to break or lose your existing seat collar. Please note that it is not compatible with the P3 Carbon, P2 Carbon, or any other Cervélo TT model, rather it's for their Soloist-series road models only.