This is a practice mute made by Schlipf. It's foldable and can be stored inside the bell. By changing the direction of the clip, it can also be used as a concert mute. By inserting the included urethane and sponge, you can adjust the blowing feel and volume of the mute. I've used it a few times, but haven't used it in a while, so I'm putting it up for sale. Currently, the retail price at a certain tuba shop is 79,800 yen. It's an expensive item, but I recommend it to those who are having trouble finding a place to practice, such as in an apartment. Wind band Tuba