This product allows me to use my Bass Trombone mouthpiece (a Denis Wick 00AL) when playing Eb Bass, which is great as it means I don't have to adjust my embouchure when switching between these two instruments. The adapter fits perfectly, on both mouthpiece and instrument, feels just as natural as using a standard tuba mouthpiece and doesn't appear to have any impact on the tone or tuning of the instrument. It's not so great for playing BBb Bass but that's completely down to personal preference of needing a bigger mouthpiece overall for that instrument. The adapter still performs it's job perfectly on both tubas and some players may be happy playing BBb Bass with a Trombone mouthpiece. Overall, the adapter does the job it was made for and is an ideal accessory for players needing to switch between trombone (or euphonium) and tuba. It's also a lot cheaper than buying a separate tuba mouthpiece!