1.I’m sure it’s glass - when I clean mine with isopropyl alcohol they make that ‘squeaky’ noise you get with glass rather than plastic, and they’re more resistant to scratches than most plastics are. According to manufacturer website K & F use German optical quality glass so I’m sure they would have been called out for that a while ago if it wasn’t true 2.I drop one last year and it broke like glass ..I’ve found them easy to clean and well made. 3.Looks and sounds like glass to me 4.HD optical glass 5.As far as I can tell it is glass. Excellent optical qualities 

Yes, can and I do. 

Yes,it can 

Hi, the frame made by aviation aluminum. 

Hi, we checked the fe 24-70 mm f2.8 g master lens size is 82mm, please reconfirm the lens size , for the filter only related with lens size , not related with lens brand, just select the same size filter with your lens, thanks.