I got these for my KEF LS50 speakers, and later my stunning Harbeth P3ESR XD Monitors.
I learned later that the Harbeth speakers should be on an open frame speaker stand, like the IsoAcoustics, so I switched.
These are in excellent condition with only minor wear.
The bottom is a thick layer of medium density open cell foam, then a beefy steel plate for weight, and a thin layer of denser surface foam with great grip to keep speakers in place.
An excellent solution at a fair price.
I think these are the RX5 model, which is $127 on Sweetwater. They are probably best for desktop speakers or small studio monitors that need isolation.
Pickup in the west village on West street, weekdays before 2, anytime on the weekend.
See the map on Craigslist.