well i have two sets of glass as well but you have to find someone who has one when yours brake since most glass shops dont carry it or they will bring out a mustang rear and it dont fit. not problematically rare but harder then just calling up the glass shop and have them install one like the fronts. course they dont brake as often so it is up to an idividual i hang onto stuff more than most just in case type attitude and if you have an extra its always nice. course with this site and ebay it makes finding those things easier but you still have to worry about shipping.