Product review (3 stars): The couplings work, are required, but lack longevity
I would give this part 5 stars if it lasted more than 2 years, but it does not.  There is something peculiar with the rubber parts in the world today.  After a certain amount of time, usually ranging from 4+ years, the rubber seems to get gooey and soft.  I have had this happen repeatedly with my Kitchen Aid drive couplers...and they don't seem to try to fix the rubber formulation at all.  I think this is their way of getting a prolonged source of recurring income by selling these defective rubber couplings.  It drives me nuts.  I love my Kitchen Aid blender but hate the drive couplings.  BTW, making smoothies using use cubes seems to be REALLY hard on these couplings.