About this item Large size: This package contains two different sizes, 30mm, 40mm, larger size allows you to put in place in one step, the two sizes can overlap seamlessly. Materials: Woven carbon fiber, woven carbon, heat-resistant, impact-resistant, sturdy and durable, beautiful appearance, light weight. Feature: Carbon fiber headset spacer resistant to corrosion, more sturdy, durable, Lighter and harder than aluminum alloy headset spacer. Appearance: automatic cutting, all sizes can be stacked seamlessly, smooth edge, delicate texture and durable. Compatible Dimensions: The inner diameter is about 28.6 mm, the outer diameter is 34.9 mm, the total weight is about 35g. Perfect for most mountain bikes, road bikes, and 28.6 mm front bar fork bikes.