Sound boosters for instruments with rotary valves, a set of two narrow-type boosters. As shown in the example, open the rotary valve cap, 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 depending on which valve you put the booster in. It might sound a bit dubious, but please give it a try. We offer three sizes: 【Narrow】, 【Middle】, and 【Wide】. The effect tends to increase with size, but stronger isn't always better, and the best condition varies depending on individual condition, instrument compatibility, etc. We also offer a 【Powerful】 version, which has a different resonance. We hope you'll try various options and find what works best for you. ※Please note that the perceived effect may vary from person to person.