This is a simple key-shaped wrench for M3 nuts, for those times when space is cramped. The socket is 14 mm deep.
The model was made with tolerances that work well for one of my print profiles. You can print the first few millimeters of the model and then abort, to see whether the fit is right. You can either scale it in the XY direction or use XY size compensation in your slicer program if you need a tighter or looser fit.
You can also scale up the model to about 134% if you want an M4 wrench. You can obviously scale it up to any size, but above M4 it will become large and therefore less practical.