Expansion Woes

My my, have you ever worried about how things expand when heated? I once explained this to one of my friends in Physics in my first year of University, and looking back now, it’s rather interesting. The question he asked me was:

“Eh, if you got this ring right, when you heat it and it expands… what will it look like?”

Oh yes, he asked me with reference to this diagram:

And I wonder... Mmhmm...