I have a fairly old cello (in a cheap rather than antique way) with a solid steel endpin.
I am not sure if there is any industry standard in cello spike tip sizes, but when I saw the size of this stopper I thought that it wouldn't fit on the tip of my cello spike.
As it was under one Euro, I thought I would try and jam it on anyway because I wasn't going to return it. To my surprise it expanded and fit on... albeit tightly and somewhat awkwardly.
It grips carpet, but I think it would be better for a hard floor where the tip was a bit bendy allowing it to be anchored a bit better.
Every cellist should have one. It is only 79 cents or something, why not?