The first Gramma I purchased was to use underneath a subwoofer in a 5.1 home theater/audio setup. This product really does a great job of isolating and tightening up the notes from the subwoofer so that what you hear is real bass and not something that is affected by the floor.  Next I bought one to put underneath a stand for my audio and video components. I know that sounds crazy and maybe it is, but I wanted to isolate everything from the vibrations on the floor. I really don't know if that makes any difference sound-wise since I didn't do a comparison, but I feel better knowing the stand is resting on a Gramma instead of directly on the floor.  My third and fourth Grammas were purchased to go underneath left and right studio monitors used to amplify electronic drums when I want to hear them without using headphones. Again, they do the trick of isolating the sound so what you hear comes from the speakers and not impacted by the floor. They are very sturdy and the claim that they support 300 lbs seems accurate to me. My only complaint is that these are pretty expensive considering one could probably make something like this for a lot less money, but since I am a klutz when it comes to making anything and am lazy as well, to me it is worth spending the $$ for one of these. Or four.