According to BMW's ETK, the rear sway bar is 33552283655 with an outer diameter of 22.5 mm.
Same part number from MY 2008 to 2012.
According to the parts catalog for M3 GT4, the rear sway bar is 33508321821 with an outer diameter of 22.5 mm.
So, given that OD is the same, perhaps the ID and/or shape is different?
