Now that I have your attention, I have carried this tool in my backpack for at least 10 years and it is a thick rubber band. Usually I use it in cold weather to act as a gripper on a filter rim when the filter sticks to the lens and I can’t unscrew it. Take 5 minutes to try it and for ever and ever it will be in your backpack.
Love the tips and tricks! I don’t know, but it might even keep your fingers from sticking to a metal filter if it’s super cold and damp. I’m not that adventurous so I won’t be finding that out! Ha ha I did use one on a very used zoom lens that got loose and would zoom out if I tilted it down. It kept me shooting for quite awhile until I got a new lens.