Russian term (edited): ������ �������

A tricky part about using "refill" here is that it can be easily confused with the cartridges used for some (even gel) pens. In this case, the speaker definitely refers to the disposable refills you insert into the pen - the idea, I suppose, is to push out the tip, attach a needle, and a piston on the other side. Perhaps those chaps are even using the original tip (sharpened, or as-is) for improvised needle, that I don't no (nor really want to).
So, if there is an English word (which I'm not aware of) that discriminates between these different types of refills, I'd use this one instead