Features: Adopt anodized oxidation treatment in the surface layer to prevent the rear derailleur wheel from rusting and oxidation. With the characteristics of anti-deformation and wear-resisting, it is sturdy and durable and has a long service life. Description: Name: Pulleys Guide Material: ceramic/steel Material: Aluminum Alloy, Metal Features: High Strength, Anti-rust, Corrosion Resistant Size Details: 11T: Diameter: 3.4cm/1.34" (Approx.) 13T: Diameter: 5.1cm/2.01" (Approx.) 15T: Diameter: 6cm/2.36" (Approx.) Packing list: 1 x Pulleys Guide Note: Different displays may cause the color of the item in the picture a little different from the real thing. Manual measuring,please allow 1~3mm error,thank you. --With deep tooth design, the rear derailleur guide wheel can fit closely with the chain, reducing chain wear, not easy to drop the chain, and improvingefficiency. --Made of premium aluminum alloy and metal material, the rear derailleur is high hardness and corrosion resistant. --There are three different sizes for you to choose: 9T,11T, 13T, 15T. --Universal for mountain bikes, road bike, folding bike, etc.