My PowerBlock weight insert “Selector Pin” broke. The part looked pretty basic so i decided to model it and print it. I re-used all of the old hardware from the broken insert. It came with some magnets and some torx bolts and nuts. Works good.

I printed with PETG. 6 perimeters. 25% infill. Seems to hold up just fine. (A hard TPU shore 98 or something like that would probably do great in this application as well. I haven't tested that filament though).