Bach Bass Trombone Mouthpiece Silver Plated, Large Shank ★1-1/2G Cup Diameter 27.0mm ★1-1/2GM Cup Diameter 27.0mm Set of 2 ★Purchased new for comparison and in excellent condition, each used only once for testing. Likely manufactured in recent years. *Will not be sold separately. 1-1/2G A standard basic size that has been used as the standard bass trombone mouthpiece for many years. It is favored by many veteran players, and is also suitable for beginners and junior high/high school students. 1-1/2GM While having the same rim and cup as the 1-1/2G, this model has a longer throat and a wider backbore, resulting in a slightly more open sound.