Note: Please refer to the diameter marked on your seatpost to determine the required seat clamp size.
For seatposts marked with diameters 27.2mm or 28.6mm, choose the 31.8mm seatpost clamp (not suitable for fixed-gear bikes).
For seatposts marked with diameters 30.4mm, 30.8mm, 30.9mm, or 31.6mm, choose the 34.9mm seatpost clamp.