1. Electrochrome is the one for auto-dimming mirrors, with shiny black plastic housing.
2. Bright black is same as electrochrome, but without the auto-dimming. The black plastic housing is of shiny material (used to come on X5's with Sport Package only).
3. This one is the one with auto-dimming but not for vehicles with Sport Package.
4. This one is no auto-dimming, non-shiny black plastic housing.

You will need to find out whether you have the shiny black plastic mirror housing and if your X5 has auto-dimming mirrors. Then order the appropriate parts. The rule of thumb is if you have Sport Package, you have the high glossy window and mirror housing trims. Otherwise, you don't.