This is a rim for practicing and checking your trombone embouchure. You can check the shape and movement of your mouth in front of a mirror. It's an item to check what kind of embouchure you use when playing and to help you find the best method. I bought this over 20 years ago and have been storing it at home. I used it when I played the trombone in the school band, and it has been cleaned thoroughly. Please refrain from purchasing if you are concerned as this is a used item.