I have 50% tint on my E39 and I think it is just a little too dark. It is Jet Black with a black interior so that may add to the darkness.

Since most X5's come with factory tint, I would only go with a 50% in the front. I'm not a fan of the blacked out look so the slight difference in tint for the front would not make it look too bad. 50% did cool my interior down a lot though.

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