Sound boosters for instruments with rotary valves, a set of two thick types. As shown in the example, open the cap of the rotary valve, place the booster, and then close the cap. The gold one makes the sound wider and more resonant. The silver one sharpens the sound's contours. If you put both in... The resonance changes even if you change the valve where you put the booster. We offer three sizes: 【Narrow】, 【Middle】, and 【Wide】. The effect tends to become stronger as the size increases, but it's not necessarily better to be stronger. The best condition varies depending on individual condition, compatibility with the instrument, etc. We also offer a 【Powerful】 type, which has a different resonance. We hope you will try various types and find your own best. ※Please note that the perceived effect varies from person to person.