The boot floor cover was made of lightweight fibre-board (not cardboard as infamously described on the Top Gear television show). The CSL discarded a large proportion of the M3's sound insulation, the electric seats, the navigation system, the air conditioning and the stereo (the latter two were able to be re-added as no-cost options). The interior includes fibreglass front racing bucket seats, a fibreglass backing for the rear seats, and carbon fibre for the centre console, door panels, door trim and head-liner. The steering wheel has just a single button which activates the M track mode, instead of the buttons for cruise control, stereo, and phone controls on the regular M3. The CSL retained the 50:50 weight distribution of the regular M3.