Crank description: Brand: BUCKLOS Crank Arm length: 170mm Material: AL6061 aluminum alloy Compatible: Single/Double/Triple chainring; for 7/8/9/10/11S chainring Bolt Center Diameter: 104mm BCD Weight: about 707g (right & left) Advantages: light weight,stylish appearance,very cool,high strength axle,strong compatibility Chainring : Brand: BUCKLOS Material: 7075-T6 Aluminum alloy,Titanium plating Size: 30T,32T,34T,36T,38T,40T,42T Compatibility: 8,9,10,11 speed chain Bolt Center Diameter: 104mm BCD Thickness: 4mm Shape: Round/Oval Color: Black, Red Round Weight: 38g/32t,about (different size,different weight ) Fit for MTB Bike,XC/Off Road/AM bike modified single chainring. Package:1pc Crank+1pc Chainring+4pcs single speed Bolts(gift)/1pc Crank+4pcs single speed Bolts(gift)/1pc Chairing.