drawing shows both 1/4" and 6mm as the dimension D. It can't be both.
6mm = 0.23 inches
1/4" = 0.25 inches
A knob for a 6mm shaft does not fit fit on a 1/4" shaft.
Conversely a knob for a 1/4" shaft CAN be put on a 6mm shaft.
Which are these? Who knows...