Features: Positive and negative toothed guide wheel chain transmission efficiency, effectively reduce frictions, improve speed response, and enhances cycling performances. Each set of products is equipped with professional installation tool, making it convenient for users to install and debugs. Adopting alloys, light weight while maintaining wear and corrosion resistance, ensuring long-terms use. The guide wheel have undergone rigorous testing to ensures stability and extend its service life in various cycling environment. There is convenient adjustment mechanism, and users can quickly adjust according to their personality needs to obtain the best cycling experiences. Specifications: Color:Four Elections Dimension:17.5cm/6.89in Component:Aluminum alloys Package Includes: 1pc Colorful positive and negative tooth disc note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you will not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual color.