1Adopting aluminum alloy and ceramic material, this product is very durable to use. 2Can be applied for most mountain bike. 3Supporting for various speed shifting. 4Suitable for use 4 / 5 / 6 mm guide wheel screws. 5Offers you a better cycling experience. Features: Adopting aluminum alloy and ceramic material, this product is very durable to use. Can be applied for most mountain bike. Supporting for various speed shifting. Suitable for use 4 / 5 / 6 mm guide wheel screws. Offers you a better cycling experience. Specifications: Item: Bike Guide Roller Material: Aluminum Alloy + Ceramic Colour: Black, Golden (Optional) Diameter: 4 cm / 1.6 inch (11 T), 5 cm / 2.0 inch (13 T) Weight: 21-23 g Package Included: 2 *Bike Guide Roller 2 * Installation Hole Adapter Tubes (Other things on the pictures are not included)