A plunger to fix the broken one on SECO surveying rod holders. The stock holder is either metal (doesn't break) or a poor quality plastic that does break. This is for a metal print that should last a lot longer than stock. The screw hole is printed at the drill diameter for the tap for a 4-40 thread 0.0860". All you should need to do is tap it. Normally I would suggest a Helicoil insert, but, there isn't a lot of material outside of this hole and once set it really doesn't need to come out again. The printed stainless is hard, but, with cutting oil and a good tap, you can tap it.
I made the head smaller to avoid material for a metal print, it would work in plastic as well. The stainless prints tend to have a rough texture and might need some clearancing for a good fit with a file