Trombone Large Shank Mouthpiece 〇YAMAHA 51C4L 〇YAMAHA 51C4L-GP These are the two sets. The silver-plated one has a dent in the backbore. I didn't feel much of an issue when playing, but please refrain from purchasing if you are concerned. The gold-plated one has been handled by someone else once. I am selling it because the YAMAHA 51C4L type doesn't suit me personally. Please purchase only if you understand the above. After protecting it as much as possible with packaging and air bags, I will ship it in a post-type cardboard box.