This is the lower part of the rear diffuser (so you will need the upper part of the M Performance bumper trim to fit it to), which came in black plastic and has been painted gloss black by a bodyshop. It was on my car for about 4/5 months so is not in brand new condition but is in very good condition.
Part number: 51192412406
Looking for £175 delivered.
It comes with 2 nuts and 2 bolts which attach it to upper trim piece at the bottom left and right corners.