I bought a two-pack of GNC bottles for $7 and today, one of the bottle's rubber seal got caught on the edge of the bottle while I screwed it on tight, causing it to break apart and mix with the shake itself. As I was drinking it, I found a long piece of white rubber that I initially thought was a worm. Needless to say, I'd like to stay away from GNC bottles now. What's a good shaker bottle? One that is easily cleaned by hand.