The factory tint in my 2003 4.4i is medium tint, not sure what % that equates to, but I took it to a tint specialist and he matched it up and told me it was medium tint ( I had the two front door windows done to match the factory tint. Cost was 70 bucks total. I prefer the uniform look so just ask them to match if that's what you want.

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2003 BMW E53 X5 4.4i - M62 engine (Non Sport with Premium and Cold Weather Package)
Color: Steel Gray Metallic
Mods:4.6is Exhaust (Pipes, Mufflers and chrome oval tips) BMW Sport package Taillamps, BMW Tire Valve Stem Caps
Medium tinted front windows
JVC HD Radio
Alpine 4x100 channel Amp
Orion 600W Mono HC Amp
Three 12" Sony Xplode in subwoofer enclosure