Made of premium aluminum alloy, CNC machined and electroplating process - bright, corrosion resistance, -light but high strength Specifications: 50T 52T 54T 56T 58T; standard 130mm BCD; 170mm Crank Arms Narrow wide tooth design increase the contact area with the chain greatly Comes with 5 bolts for easy and convenient mounting Specification: Teeth Length: 7.2mm/0.28 inch Thickness: 4mm/ 0.16 inch 50 T: Diameter: 208mm/ 8.2 inch 52 T: Diameter: 216mm/ 8.5 inch 54 T: Diameter: 224 mm/ 8.8 inch 56 T: Diameter: 231 mm/9.09 inch 58 T: Diameter: 242 mm/ 9.5 inch Package Includes: 1 Piece Bike Chainring 1 Pair Crank Arms (left and right) Note: The chain must be lengthened if the larger chain ring is replaced. Please allow 1-2mm differences due to manual measurement. When choose large chainring, please confirm that whether its diameter is within an appropriate range, otherwise it will need to replace a longer axle.