Lexan / PVC.
Don't build our own but they come with Lexan / PVC and that's what we would want anyway.
A few of our girls can (at times) face plant hard against the "glass" on feed day while they are in shed....hard. Usually the most aggressive feeders. They just see a heat signature and can't see that its the feeder, not the feed.
Had a big girl damage a piece bad enough last year that it needed replacement. It might have shattered if it was real glass. Assuming this is safer for the animals that real glass. (assuming)
Also depends on the animals type Snop.
The suspect on this end was a 3,400g female B.P. so I wouldn't trust her with real glass anyway.
Heather and Chris