Sound boosters for instruments with rotary valves, a set of two of a moderate type. 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 makes the sound's contours sharper. If you put both in... The way the sound resonates changes even if you change the valve where you put the booster. We offer three sizes: [Narrow], [Middle], and [Wide]. The effect tends to increase as the size increases, but it's not necessarily the case that stronger is better, and the best condition varies depending on individual condition, compatibility with the instrument, etc. We also offer a [Powerful] type, but this has a different resonance. We hope you'll try various options and find what's best for you. ※Please note that the perceived effect varies from person to person.