Features: brand new and 6061 aluminum alloy, suitable for carbon fiber or aluminum or iron for head tube. Standard 1 1 or 8 28.6mm for head tube, standard M6 screw. Applicable pipe diameter: min. 23.5mm max. 25.8mm. Easy to install.There is no need to use professional tools or force to knock in, as long as the hex wrench is screwed in. Replaces conventional star nut and top cap, a must for bike steerers. Specifications: Color: black, red, blue, gold Material: 6061 aluminum alloy Compatibility: Standard 1 1 or 8 28.6mm for head tube, standard M6 screw Applicable pipe diameter: min. 23.5mm max. 25.8mm Weight: about 30g Note: Transition: 1cm=10mm=0.39inch Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package includes: 1 Headset Expander Top Cap