mini coupling

A coupling that is as small as possible for my 3d printer.

There is a coupling and a hole. You substract the hole from the pieces you want to couple, then print a coupling, insert coupling to attach the pieces. Like this you can make overhangs, ... and have things nicely fitting, eg to try things, or to easily apply glue. Two examples of use are visible in the example, but this thing is the coupling, not those examples.

I need this to connect small pieces for another thing, that will com