Hole diameter is 19mm good for ½" EMT from home depot which is 18mm OD.
Recommend to print in ABS or PETG.
Added also a compliant based clamp for the pipe which worked better for me and holds more tightly without a screw violently pushing the pipe if not needed.
The author remixed this model.
Better printability
Included CAD model
Uses chamfer instead of fillet