Fitted to allow the 2010/11 8P RS3 to comply with ECE-26/regulation-no-26-03/external-projections/ that states:
"2.7. "Extreme outer edge" of the vehicle means, in relation to the sides of the vehicle, the plane parallel to the median longitudinal plane of the vehicle coinciding with its outer lateral edge, and, in relation to the front and rear ends, the perpendicular transverse plane of the vehicle coinciding with its outer front and rear edges, account not being taken of the projection:
2.7.1. Of tyres near their point of contact with the ground, and connections for tyre pressure gauges;"
Basically, the extreme outer edge of the tyre must not exceed the extreme outer edge of the bodywork and so, to accommodate the 8J rear wheel and 225/35 tyre as fitted to the then limited volume 8P RS3 these £s cheap items were added; it saved meaga £s by NOT having to modify the STD 8P body shell for a limited production run of 8P Rs3s (250 UK cars was the expected production run). At the front, new carbon fibre wings were fitted to the 8P RS3 - Audi using this an excuse to develop a carbon-fibre wing.
Smaller wheels and tyres on an 8P S3 and so the STD setup complied.
Bet you wish you hadn't asked, but I once had to do this stuff professionally and these ECE regulations were a darn nightmare...