Features: This is a bike front derailleur ring, made of premium plastic material, sturdy and durable. Suitable for mountain bike, road bike, and other types of bikes. Lightweight, high strength, durable for long time use. 31.8MM diameter frame can be converted into 34.9MM frame. You can replace the old one, and provide the good performance for your bike. Specification:Material: PlasticColor: as picture shownDiameter: 3.7cm/1.5inchPackage List:2 x Front Derailleur Conversion Shim