Yeah, and with any glass over about 3 inches under vacuum, it gets encased in some form of shielding, else you will NOT like what happens if you induce a stress fracture.

Also the glass is scary when you have to lift a big bell of it. My coworker thought setting the bell in a sink, so it could roll, was a good idea, wrong...
Calling around 4 years ago, that size bell of glass was 4-8K $$ , making the steel one became obvious at that point.

Steve