Box One Single-Speed Aluminum Cogs are 7075-T6 aluminum alloy. It's designed to fit Shimano compatible cassette hubs and has a 5mm wide inner base, giving a more solid interface with the cassette body. The alloy cogs are anodized black with laser-etched graphics. FEATURES - Shimano Compatible Driver - 7075-T6 Alloy - 3/32" or 1/8" Chain Compatible - Lightweight SPECIFICATIONS - Material: 7075-T6 Aluminum - Process: Laser-etched logos Weight - 13t: 8 grams / 0.3 ounces - 14t: 11 grams / 0.4 ounces - 15t: 13 grams / 0.5 ounces - 16t: 14 grams / 0.8 ounces - 17t: 16 grams / 0.6 ounces - 18t: 18 grams / 0.65 ounces