Acceptable materials to use as a homemade hop-up nub?

So I've been experimenting with homemade nubs lately and throwing ideas around in my head. So far I've tried nerf foams(works okay, but everytime I turn my hop-up on I have to re-zero my scope). I've been working on cutting a pencil eraser properly, but have to to try it.

I was wondering if sturdy paper would work? It would be easy to shape into the cylindrical shape and easy to cut. I also just read in another thread about using thick wire, which sounds feasible. I've also thought of using a shoelace.

What materials have you guys made a hop-up from? How were the results?