Ktone Gold Trumpet Mouthpiece, 8 Sizes, Convertible, New Gold Trumpet Mouthpiece 8 sizes convertible 2 Rims & 4 Cup Size ( Stamped 3C, 2C, 3B and 2B), similar type size for Bach ( 7C, 5C, 3C, 1 1/2C ) It is computer-aided design system and computer controlled lathe work together to produce the most precise mouthpieces