Here's "The Palm reader' installing his new rear window on his 68'WannaBee using an AMD brand replacement.
He weighed it along with the stock original window. The AMD unit was a whole pound and a three quarters lighter at 20 Lbs where as the mother mopar window was 21-3/4 Lbs.
Wrong area of weight removal for a stock chassis car, but it all came by virtue of having to change in a new glass anyway.