Do you just want the front to match the factory rear. If so it would be about 35%. Or you could do it all around. That is what I did, check out my X page for pics.

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2011 X5 35i Space Gray/Black Nevada Leather w Dark Bamboo Trim
Convenience Pkg/Running Boards/Cold Weather Pkg/Comfort Access
3rd Row Seating/20% Tint/Style 215 wrapped with Toyo Proxes ST II/ LUX v4

2001 X5 4.4i TiAG/Grey Leather-Retired
djbock's Custom X Page!