I believe they use H3 based HID capsules and the harness connects to the rear of the bulb.

Some of our more detail-oriented members have utilized the OE plug on the light housing, which requires a bit of wiring work but is doable.

Most just make a hole in the rear of the housing for the wire to pass through and seal around the wire with some silicone sealant.

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04 X5 3.0i auto
03 X5 4.6is