It does what it says on the tin - adds weight to Brand mouthpieces and helps add core and focus to the sound as a result.
As I bought it for this reason (to improve my Brand 16E outdoors/Xmas carol's mouthpiece) it's a great bit of kit and does exactly as expected - the orange plastic section is tapered to provide a good grip onto the shank and the steel barrel can then be tightened snugly up against the underside of the rim.
Had I bought this to use on metal mouthpieces by other makes, I might have been a little disappointed... As far as compatibility with some common mouthpieces in my collection goes:
- Bach - not compatible
- Schilke - compatible (just!!)
- Denis Wick (classic) #3 - not compatible
- Denis Wick (classic) S - compatible (just!!)
- GR - not compatible
- Warburton (standard shank) - compatible (just!!!)
In all this, it's simply that details on the shank prevent the orange insert from seating snugly - in theory this could be remedied by modifying the orange insert, but who wants to do that on an expensive booster???
In summary... Great on Brand mouthpieces, but be wary of potential incompatibilities with other makes!!