The control arm keeps the lower wheel straight and contacting the ground. This is a complete set of control arm from Genuine BMW. 

BMW
MY08-13 - 128i 
MY09-13 - 135i 
MY08-08 - 135i  
Rear Left Upper Forward
MY13-13 - 135is 
MY06-08 - 323i E9X 
MY06-06 - 325i E9X 
MY06-06 - 325xi E9X 
MY07-12 - 328i E9X 
MY07-07 - 328i  
Rear Left Upper Forward
MY13-13 - 328i E9X, F3X  
Rear Left Upper Forward ~ Body Type: Convertible
Rear Left Upper Forward ~ Body Type: Coupe
MY12-12 - 328i F3X  
Rear Left Upper Forward ~ Body Type: Convertible
Rear Left Upper Forward ~ Body Type: Coupe
Rear Left Upper Forward ~ Body Type: Wagon
MY09-12 - 328i xDrive E9X 
MY13-13 - 328i xDrive E9X, F3X  
Rear Left Upper Forward ~ Body Type: Coupe
MY07-08 - 328xi 
MY07-07 - 328xi  
Rear Left Upper Forward
MY06-06 - 330i E9X 
MY06-06 - 330xi E9X 
MY09-11 - 335d E9X 
MY07-11 - 335i 
MY12-13 - 335i F3X  
Rear Left Upper Forward ~ Body Type: Convertible
Rear Left Upper Forward ~ Body Type: Coupe
MY10-12 - 335i xDrive F3X 
MY13-13 - 335i xDrive F3X  
Rear Left Upper Forward ~ Body Type: Coupe
MY11-12 - 335is E9X 
MY13-13 - 335is E9X  
Rear Left Upper Forward
MY07-08 - 335xi 
MY14-15 - X1 sDrive28i, xDrive28i, xDrive35i  
Rear Right Upper Forward
MY13-13 - X1 sDrive28I 
MY13-13 - X1 xDrive28I 
MY13-13 - X1 xDrive35I