Locking nut. Above: previous shock absorber 1138 120 4100 with lock nut 1138 140 9500 Below: new shock absorber 1138 120 4102 with screw cap 1138 140 9300 On the new shock absorber 1138 120 4102, instead of a threaded pin, an M5 threaded bush is inserted. The air filter will be supplied in the future with the screw cap 1138 140 9300 fixed on the shock absorber. In the near future the previous screw cap 1138 140 9300 will be replaced by the screw cap 1138 140 9303 and the O-Ring 9645 951 3007 as leakage protection. Models: MS 441 MS 441 C-M MS 441 C-M RVWZ MS 441 C-M RZ MS 441 C-M VWZ MS 441 C-M W MS 441 C-M Z MS 441 C-MQ MS 441 C-MQ Z MS 441 C-Q MS 441 C-Q Z MS 441-RVWZ MS 441-RZ MS 441-VWZ MS 441-W MS 441-Z