Hey guys thoughts on glass rear fenders

 

The main advantage is that you can get then 3" wider than the originals in case you like fatter wheels/tires in the back. There's also a slight weight savings over steel fenders. The ones I got from Bebops had to have some body work done to them to bring them up to the standards of new steel fenders. You'll have to drill your own holes in them to mount them.

 

Just like anything, there are good ones and not-so-good ones. The last set I worked on had a relatively good fender on one side and a wavy one on the other. Since the weight of the fender is dependent on how much fiberglass the guy sprays into the mold, you will find some that are thin and light and others that are thicker and heavier.
Since you asked the question I have to assume that you are considering the purchase of FG fenders. There are many pros and cons, and depending on where you live, the value of each may vary. Here in SoCal there is not too much concern about rust-out from road salt but there is an effect from lots of sun and heat. I guess that you will have to weigh what's important to you when you make your decision.