Product review (5 stars): Stop looking...this is the one you want.
I must be nuts to have spent a bunch of time reviewing a bunch of these inserts, but, hey, that's just who I am.  So, I decided on this one and that was the right choice. It literally took seconds to pop the thing in, it fits perfectly, and instantly my disposal went from the obnoxiously loud monster it was to a quiet hum, and I no longer had to enjoy that lovely experience of water splashing all over me when I turn on the disposal.

The original one had just worn out over time, and I didn't want to have to take the whole thing off to install a new rubber one.  This is the way to go, trust me.  So much so that I ordered another one just now so that when the one I have now goes bad in a few years, I don't have to try to re-find this item.  100% happy with this item.