Mountable Duct Adapter

This is an adapter to connect a 4" duct to a 3" duct. The adapter has mounting holes, and is designed to be mounted to a 2x4.
The model is adjustable (in OpenSCAD), but has only been tested for this use case.

I used a flexible duct on the small side (going to an air purifier) and a semi-rigid duct on the large side to make a posable fume extractor.

Because of the small print volume of my Monoprice Select Mini V2 (100mm cube), I had to split the model into 3 pieces to print. You can download these three pieces, or the full model as STLs, as well as the OpenSCAD file.