The arm rests on my office chair (Hyken chair, Item # 23481, SKU # 990119) were coming apart, and the non-standard screw hole placements made finding online replacements impossible. So, I took them off, traced them, imported the trace into OpenSCAD, hulled them, fine tuned the dimensions, extruded them (with a little bit of a curve), differenced out the screw holes and the bottom apron, flipped them over in Cura, and printed in TPU with 8% gyroid infill. The give on them is about the same as the originals, but they will probably outlast the rest of the chair. All for about $3 worth of TPU plus electricity (and my time).