These stoppers are designed for a step drill set with 4-12, 4-20 and 4-32 mm. On usage the side with the figures must be oriented towards the machine. If a stopper sits too loose on a drill it can be fixed with a 3 mm screw. Either use a screw with self cutting thread or cut a M3 thread in a hole on the side.
The stoppers can be stored in the drill box. A small fence that can be glued into the box separates stoppers and drills (at least when the box is kept horizontally).
The author marked this model as their own original creation.