When We wintered in S Texas our lot was situated where the rear window wasn't in the full sun.Our friend had a roll up just like the one I posted and his rear window was in the full sun and he used his screen almost daily.Some people had large side windows with shade on them to keep the hot sun out for a few hours each day.If our space was turned around or we had a different lot then my rear window would have a shade on it,either a roll up or a removable.I don't have one but I know they work by talking to the people that bought them once they got down there.