MATERIAL QUALITY:Made of premium aluminium alloy, lightweight, high strength and deformation resistance, durable for long time use. CRANK ARE LENGTH: 170mm crank arm length without any overlap of crank arm and chain ring bolt. PERFECT CUTTING: Standard quality cutting of hole, which ensures to bike, easy to install. Spindle Interface Type: Horizontal Square Taper. Please check if the orientation of your right crank is rhombic. Keep both left and right things having the same hole. Suitable for road bike, mountain bike, folding bike, fixed gear bicycle, etc. Material:Aluminum alloy colour:Black Package Contents: 1 pair x bicycle crank arms Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.