Features: Make from high-strength aluminum alloy, not easy to rusts, ensuring durability. With a chain mud and dust proof designs to maintain perfectly chain performances. Enhances chain efficiency by reducing wear, prolonging chain lifes and reducing noise. Suitable for mountain bike, road bike, folding bike. it can also be used as a replacements for your old or broken chain. Simple to install, light in weight, and small. No more worry about the chain falling down during Cycling after installation. Specifications: Materials: Aluminum alloy Styles: 2/1 Size: as shown in the picture 1 support tooth disc ranges: 30T-40T (round disc), 30T-38T (elliptical disc) 2 support tooth disc ranges: 28T-40T (round disc), 30T-38T (elliptical disc) Package Includes: 1pc Mountain Bike Chain Guide note: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.