An adapter for connecting pipes with different diameters. The code lets you customize resolution, inner radii, height, thickness, straight parts at the ends and rounded edges. It is designed to also work in Thingiverse Customizer - deadly slow (to speed it up, you can set a low fn-value, until you are done), but it gets you the job done.

In any case it is better to open it with OpenSCAD, where any version up from 2015 should work and any version up from 2016 supports a Customizer. Just open the .scad file in OpenSCAD, display the Customizer window, choose your settings, and press F5 for view F6 for STL generation and finally F7 for STL export.