If you have a carbon rail saddle that will not fit into the clamping jaws of the original ZX-1 EVO seatpost, you will need a specific fitting kit. This kit allows the more oval shape of carbon rails to work with the ZX-1 EVO aero seatpost. Simply disassemble the hardware on top of the carbon seatpost and replace with the items supplied within this kit. This should allow you to fit 99% of carbon railed saddles on the market to your bike.