There should be brackets you can buy. I believe they stick to the inside of the bumper to hold the PDC sensor.
AW/Terra | ZSP | ZPP | ZCW | iDrive | CA
Mods: BC BR | Blacklines | M-tech rear | dual exhaust | M3 steering wheel | BMW SSK | ZHP shift knob | High-kick CF spoiler | NBT Retrofit
Varrstoen ES1 19x9.5+20 Front, 19x11+25 rear