Did you notice in the diagram the #18 & #19 are different? The little articulating arms are on different sides of the sensor...so that is probably the reason there are two different part nbrs for the rear suspension. Then when you look at item #20...these are the brackets for the level sensor and they have two different part nbrs and are identified as being for the left & right.
If you still have doubts...simply call your local BMW dealership’s
parts department (Not the service dept) and give them these two part nbrs. They will be able to verify that the rear suspension requires these two different part nbrs....or if you only need to buy two of one of the part nbrs (which I doubt).
