High quality large shank trombone mouthpiece by Bach. Large shank mouthpieces fit in what are sometimes called symphony tenors - horns with a .547" bore like the Bach 42. These are common in the band world, and the most common size among orchestral players. Some jazzers use a big horn too but not many. Bass bones, .560" bore like a Bach 50, accept large shank mouthpieces as well. If your trombone takes a large shank piece, this one's for you.