These are simple battery spacers that push-fit onto the positive button terminal on the top of a C-cell battery to avoid shorts and minimize lateral cell wobble when in a battery pack.

I used four of these to create a DIY four-cell stick NiMH battery pack for a portable oscilloscope with an old fried NiCd pack. I hope someone finds these useful for their project!

DISCLAIMER: I do not recommend soldering to bare battery terminals! Spend a couple bucks more and get the tabbed versions of the cell so you aren't soldering on something susceptible to thermal runaway.