Heat treated cogs are carefully machined from nickel chrome steel all of these cogs have a hardened chrome satin silver finish for longer wear each cog has an indented ramp called ultra drive ud to assist in up shifting tooth profiles are also custom configured to help with down shiftingcassette combinations of 12 23 12 25 13 26 and 13 29 the sprockets must be shaped appropriately for the drivetrain to work perfectly the end result is perfect shifting and high precision operation every