I don't know a whole lot about the process, so I'm just making guesses, but I'd be willing to bet big companies like RooR, DZL, PHX, Delta, etc., have machines do it. Those things are all exactly the same and they're all crafted to perfect, machine-like specifications. Considering how much glass they sell, they'd have to have a lot of glass blowers, and it seems pretty damn unlikely that all those people are all doing it that consistently. Besides, have you ever heard of a "factory" glass blower? Who invests all that time into the trade to be a boring, one-dimensional glass blower? I just don't see it dude. Sure, a lot of bongs are handmade, but I'd be willing to bet good money that the big guys have machines for that shit.