Well, you can't see through them so I guess they aren't really windows. I made light admittance devices for my chicken coop!!!!! I'm going to Ohio for a few days and I want to lock my chickens up while I'm gone because I suspect they are laying eggs somewhere besides the laying boxes in the coop. Hopefully being locked up in there for 5 days will retrain them to use the nesting boxes. Anyway, it's always kind of dark in the coop because there are no windows so I made "panes" out of polycarbonate and frames out of ABS. I tried a few different ways but I could not make the PC transparent. More like translucent. I'm going to have to work on that. I've seen videos of it being pretty see through. I need to buy a .8 nozzle for my next attempt.