Tool-a: suitable for using the bottom bracket with outside diameter of 44mm and 16 cogging This model is common specification of the bottom bracket ( Bb51 / bb52 / bb70 / bb71bbr60 / mt800 / rs500 Tool-b: suitable for the bottom bracket with outside diameter of 46mm and 24 notches Features: aluminum alloy design, matted polishing, precised wire cutting, fully closed occlusion, not simple to slide teeth, and will not damage the bottom bracket Suitable for bottom bracket with outer diameter 46mm 24 notches Process: heat, polishing, anodizing, Manufacturer: ZBIianxer