Feature 1This product is used for rear derailleur extension, apply mountain freewheel 11-40, 11-42, 11-46, or Shimano, SRAM, Sunrace, 40T, 42T, 46T Road flywheel. 2Expand the flywheel speed change more smoothly. 34 colors available, give your mountain bike a little individuation. 4Aluminum alloy material, CNC workmanship, solid and firm, very durable. 5Great accessory for cycling enthusiasts.Specification Features: This product is used for rear derailleur extension, apply mountain freewheel 11-40, 11-42, 11-46, or Shimano, SRAM, Sunrace, 40T, 42T, 46T Road flywheel. Expand the flywheel speed change more smoothly. 4 colors available, give your mountain bike a little individuation. Aluminum alloy material, CNC workmanship, solid and firm, very durable. Great accessory for cycling enthusiasts. Specifications: Condition: 100% New and High Quality Material: Aluminum Alloy Color: Black, Red, Yellow, Blue (optional) Size: Approx. 4.5*2.3cm/1.7*0.9' Package Weight: Approx. 12g Packing List: 1 x Bicycle Rear Derailleur Hanger