I've been using IBTanked pyrex cartotanks since they were first put on the market...some 8 - 10 months or so ago. My total just reached twelve tanks (seven 19mm and five 22mm). I own several brands of cartotanks and they are obviously my favorite. You can see most of my collection in this photo gallery
http://www.e-cigarette-forum.com/forum/members/baditude-albums-pictures-my-setup.html . These are a high quality, elegant looking, and inexpensive tank for the price.
These tanks are pretty tough. I've yet to crack one, and I'm pretty clumsy. Mine have fallen off of a dressing room bench onto a hard tile floor. Even worse, they have fallen from my lap getting out of my car and onto the parking lot. They fit very snuggly on the carto (attached to my mod) so I have absolutely no fear of carrying it in a front jeans pocket when out-and-about.
That said, they
are glass, so do try to be mindful of preventing accidents if at all possible. Should you be interested, I did a thorough review of these tanks in my blog:
http://www.e-cigarette-forum.com/forum/blogs/baditude/3318-3-ibtanked-pyrex-glass-tanks-review.html