I have an interesting story about these isolators on speakers. I was not in the market for such things until we happened upon a booth at the Toronto Hi Fi show where they had an A-B set-up with the exact same speakers, one set with these isolators installed the other with the speaker manufacturer base feet.
I was a little surprised at how it cleaned up the muddy base. I purchased the items specific to my Wilson Benesch Squre 2 speakers at a reasonable cost discount (show special). Installed them on my speakers on hard wood floors and found these cleaned up my upper base response significantly.