This Narrow Wide Chainring is made from CNC machined 7075 aluminium for enhanced durability. Simple and effective, won't let you down. Production details: Material: CNC AL7075Alumium alloy,hollow Narrow & Wide teeth chainring Color: black BCD:130mm Teeth: 50T 52T 54T 56T 58T Weight: about 85/88/92/98/103g Diameter: 208/216/224/231/242mm Full CNC made narrow-wide chainring for single ring Compatible chain speed: 6/7/8/9 speed Tips: if you replace the larger teeth chainring of your bike, the chain must be lengthened generally. Product selection suggestions: √For 14/16/20 inch folding bike, each size has a common choice for chainring teeth √14-inch folding bike is generally 47T √16-inch folding bike is generally no more than 53T √20-inch folding bike is generally no more than 56T √of course, it can be adjusted according to personal circumstances