I like this a lot, it is really heavvy though but that was what I wanted.
With this you eliminate almost all vibrations in the mouthpiece giving you more power if you need to get a high volume out of your horn. You can also play a little softer and still get a stable tone. Is it really necessary? Not really but it is fun and it helps me when I use mutes to get the tone out and to project.
I would recomend using this if you use a Yamaha silent brass mute and play soft, any booster or heavvy mouthpiece helps a bit with that system.
I wish KGU made it less sharp in the corners, I get that this is the raw finish and you can just take the corners off with something but still..
I would recommend the polished silverplated version for a more finished product though it will still look.. blocky.
This booster fits most standard mouthpieces like standard bach and the like but also actually fits many more, It fits on my Claude Gordon Marcinkiewitz no 3 mouthpiece.