This is a BEST BRASS warm-up mute. It can be used for trombone and flugelhorn. I used it with a tenor bass and alto trombone. I had one in each instrument case for practice, but I am getting rid of my instruments, so I am selling the mutes as well. There is a slight dent. Also, the sponge is starting to crack. However, it never fell out during practice. Although I haven't confirmed it, https://www.bestbrass.jp/online-shop/repair-parts/1047-sponge.html ↑ Looking here, it seems like the sponge can be replaced. Please inquire if necessary. Personally, I was satisfied with both the soundproofing and the playing feel. I live in an apartment, but I have never received any noise complaints from my neighbors, so I think it works properly. - Included items: Box