The windows on my truck were rattling pretty bad when part ways rolled down. I found out it was the hard plastic edge on the mirror cover hitting the glass. There is a rubber seal inside the plastic which should be slightly higher than the plastic, but wasn't. I measured the length of the strip, and cut a piece of 1/4 X 3/8 in. neoprene sponge weather stripping, which I put between the hard plastic and the factory seal(stuck it onto the hard plastic.) The sponge I put on fits flush with the hard plastic, but causes the factory seal to sit out against the glass rather than the plastic against the glass. No more annoying rattle!