XLC Headset Extender AP-C03 - for 1 1/8" forks with carbon steerer - for inner-22.0 - 23.4mm (without shim) - for inner-23.4 - 25.0 (with shim) - 40mm clamping height - stabilises the carbon steerer from the inside for a stem clamping that is gentle on the material - weight: 35g.