Genuine BMW part 52 10 2 695 395: Switch, backrest width adjustment, left. The number stamped on the part is 52102695395; BMW's catalog files it under the short number 2695395. You will find it on our Interior Body shelf, under Tail trim.
It fits the E46 coupe (M3, 2001–2006), with the S54 engine.
BMW draws it on 2 diagrams, among them Seat, front, lumbar (52_2791) and Seat, front, lumbar (52_3397). BMW's catalog calls for two of these at each place it is fitted. It weighs about 10 g (under 0.1 lb).
We have not had one on the shelf yet. Request it and we will tell you when one comes off a car.
