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 sharpens the sound's contours. If you put both in... The way the sound resonates changes depending on which valve you put the booster in. We offer three sizes: 【Narrow】, 【Middle】, and 【Wide】. The effect tends to increase as the size increases, but it's not necessarily better the stronger it is, and 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 options and find what works best for you. ※Please note that the perceived effect may vary from person to person.