Bill, they all have broken at an angle, not a straight break. I don't know what the deal is, or if that means anything. The one that just broke wasn't a tight fit, it was a smaller ring so the tip wasn't hard to pull out at all. Pulled the tip out, and the bottom ring just sprang off.
It HAS to be a heat thing .....
Kami - I love Vegas when it's hot ....
I've popped three of the small ones in two days. Top space, straight split. Finally gave up and am just using one!