difference between 33331118928 hard and 33331118929 Soft BMW e21 mounts

[Vincent Hill]

I have found that the Right side Rear Subframe Mount is Worn out and causing wheel movement not to mention the Squeaky sounds when it moves. I got the Subframe out but now see that there are "2" Part Numbers (Hard & Soft for the same thing. Anyone "Know" what the difference is??

My "Guess" is the Harder one is more like a Urethane with very little give and the Soft is more like rubber with more give??