Can't remember X1 off hand but all late model BMW bumpers are essentially the same or very similar to remove. 2 female torx 50 bolts from underneath. If you can't see them or reach them then the diffuser or valance should be I unclipped and removed 1st. Then remove the clips and screws on the rear wheel arch covers that are attached to the bumper and slide backwards off. When installing be careful to ensure that the slides on the bumper slide cleanly and evenly into the guides on the sides of the car. Hope that helps.
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