The color glass is a real PITA to work with! Siam was having the same problem we were. We do a batch of 100 color tanks and have a bunch of failures that come out of the oven and caps won't fit them. And even the ones that are not "failures" require different size o-rings to get the caps to work properly. I am not even sure what we will do about the amber, as our last 3 color batches have produced 100% failures for the ambers. It is very frustrating.