new this year Rohloff re designs their cog to be simple to replace in the field , with a snap ring and a screwdriver.
though their spline pattern is their own (in 13 splines to match their smallest cogs 13teeth, and all the larger sizes.)
so a flat cog is cheap to mail to you & now the chain-line for the 13t cog is the same as all the larger sizes, [ It was wider ]
too bad they didn't just use the 3 speed spline pattern .. used universally for a really long time. & cogs are Cheap.