The Aero filler cap - the fuel tank cap on the S.

R53
http://www.mini2.com/galleries/data/...e_View_Car.jpg

R56
http://www.mini2.com/images/predrive...PICT0050_t.jpg

I much prefer the original one, and was one of the first things I noticed on Launch day at Menzies that it apeared to be price driven.

BMW themselves said they weren't making enough money on the MINI per car, and it had to be cheaper.