content: Yeah, he/the title said glass lid but the intro shows him milling it and it looks like Lexan or some such plastic. After I realized it wasn't actually glass I was less worried about it. That acetylene looks like a bad idea.  He referenced another channel which called their head glass but it was Lexan or poly-carbonate also. Maybe someone will do it with Gorilla Glass or something soon but I'm sure that's a bit more difficult to machine. Looks pretty cool though. Gotta wonder how long it can last before you loose the seal.