Patience, young padawan, and read earlier in the thread. You should have pix/comparisons when Gregory in Switzerland does his DIY install. All that 'shows' in the interior is the thicker aluminum shaft above the leather boot, if you stick with the stock shifter knob. And you can certainly read all about the UUC shifter at its website and in the Pelican Parts tech articles, albeit not for the X5 specific variation of the concept. I'm not sure what you mean by 'heavier.' The machined aluminum shift knob [an extra] is certainly much heavier than the OEM plastic/wood trim knob; pushing through the gears doesn't feel 'heavier;' I expect, but don't know, that the SSK shaft is 'heavier' than the aluminum/thermoplastic OEM shifter.

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2006 X5 3.0 6-spd w/Evo UUC ssk
sport/premium pkgs
born Valentine's Day, 2006.