Just very simple end cap for RC screwdriver set that comes in 7 pieces, like this

This screwdriver set is very handy for disassemble my P1S extruder without fear stripping the hex screw, and it is a lot easier to use than cheap allen key came with the printer.

I print in PETG but any filament works. Just put some glue for it to stay in place.

I bought this set from Aliexpress for about AU$9 (shipped)