I printed this in PETG with 5 vertical perimeters so the set screws had something to dig into. Only 10% infill so the ring can be squeezed closed easily. The chamfer code is not mine… it came from an OpenSCAD project by Timewaster via Google search: https://github.com/SebiTimeWaster/Chamfers-for-OpenSCAD/blob/master/Chamfer.scad
The author marked this model as their own original creation.