SRM Shimano Dura-Ace 7900 Wireless Powermeter One Color, 170mm, 34/50 Arm Material: aluminumArm Length: 170 mm, 172.5 mm, 175 mm, 177 mmBottom Bracket: Not includedBB Type: FC-7800, FC-7900BB Threading: EnglishBolts: alloyRings: 2Spindle: Compatible Components: Weight: 820 gRecommended Use: Power training, Road racing, Road cyclingManufacturer Warranty: 3 yearsBolt Circle Diameter: 130 mm Chainring Sizes: 39 53, 34 50