The full glass coverage is exactly as it sounds, if you have a glass loss your deductible is zero. We had a customer who had some long metal pipes in the back of his truck. He was taking them out and unfortunately one went through the rear window. Oops. He had a $500 comprehensive deductible with the full glass coverage endorsement. The new window cost him nothing, If he did not have the full glass endorsement the window would have cost him $500. Needless to say, he was glad