Features1HIGH HARDNESS: Bike Chainring is made of aluminum alloy, which is much harder than the original steel sprocket. 2HIGH ACCURACY: The 104BCD sprocket adapter adopts aluminum alloy CNC cutting to ensure the accuracy of product use. 3HIGH PERFORMANCE: This round sprocket adapter effectively protects the bikes from scratches, prolongs wear life. 4PORTABLE: The Bikes Chainring is lightweight, durable, easy to carry and easy to install. The surface is easy to clean. 5COMPATIBLE: 104BCD conversion base is , compatible with Bafang electric bike mid drive motor BBS01 BBS02.SpecificationItem Type: 104BCD Sprocket AdapterMaterial: Aluminum AlloyBCD: Approx. 104mm/4.1inSize: Approx. 74mm/2.9inFits: 7 8 9 10 11 SpeedsPackage List1 x104BCD Sprocket Adapter