Circles…gallon jug rings. All thru high school my dad would hide these in my books when I brought them home and then put them back in my backpack. So when I opened my book in school these milk rings would fall out and embrass me. We are still collecting them and trying to get each other. I have a whole 5 gallon (I think) bucket full of these. I need some REALLY great idea at how to get my dad with these. Any ideas? lol. In the meantime, I will continue to collect these.