Features: and high quality Made of 6061 aluminum alloy, compatible with carbon fiber, aluminum, or steel head tubes Standard 1 1/8 inch (28.6mm) head tube size, uses standard M6 screw Fits steerer tube inner diameter: min. 23.5mm, max. 25.8mm Easy to install no professional tools or hammering required; simply tighten with a hex wrench Replaces traditional star nut and top cap, ideal for bicycle steerer tube setup Specifications: Color: Black, Red, Blue, Gold Material: 6061 Aluminum Alloy Compatibility: Standard 1 1/8 inch (28.6mm) head tube, M6 screw Steerer tube inner diameter range: 23.5mm to 25.8mm Weight: Approximately 30g Note: Measurement conversion: 1cm = 10mm = 0.39 inch Please allow 0-1cm measurement tolerance due to manual measurement Due to monitor display differences, actual color may vary slightly from the image Package Includes: 1 x Headset Expander Top Cap