glass. It is a lexan type window covering for the side windows, the rear hatch window, and the windshield. If sincerely interested, contact him and see what you can work out. This results in a fairly serious weight savings (especially compared to the glass on the T-tops), but on a single set-up is pretty pricey. The more units produced, the more reasonable the price. I'd E-mail him if you are seriously looking for some significant weight savings. Other members have also expressed interest. Take care, Mark