Standard Series Trumpet Mouthpiece in Silver Group II Specifications:

• 15A4a: 17.14mm, .675 inch cup diameter; 27 throat. A larger diameter mouthpiece with a shallow A cup and tight a-backbore for upper register playing. Number 4 semi-flat rim offers comfort in upper register.
  15A4: 17.14mm, .675 inch cup diameter; 27 throat. Same as the 15A4a but with a larger c-backbore for an open feel.
  15B: 17.12mm, .674 inch cup diameter; 26 throat. With the same diameter as the model 15, this mouthpiece includes B style cup which produces a more brilliant sound than the standard model 15 mouthpiece.
  15: 17.12mm, .674 inch cup diameter; 26 throat. An excellent all-around mouthpiece which offers a free blowing, clear sound.
  15C4: 17.14mm, .675 inch cup diameter; 26 throat. This mouthpiece is similar to the model 15 but with the number 4 semi-flat rim for increased endurance.
  16B4: 17.20mm, .677 inch cup diameter; 26 throat. Same as the model 16C4 except the shallower, medium-small B cup offers more resistance, providing a brighter quality of sound. The 16B4 is an excellent choice for Eb trumpet when a player requires a bigger rim diameter.
  16C4: 17.20mm, .677 inch cup diameter; 26 throat. Similar to the 16 in dimensions, this mouthpiece offers a number 4 semi-flat rim for a more traditional feel and increased endurance.
  16: 17.20mm, .677 inch cup diameter; 26 throat. This medium-large diameter mouthpiece produces a full, free blowing quality.
  16C2: 17.20mm, .677 inch cup diameter; 26 throat. This model offers the same options as the model 16, but instead offers a number 2 rim for increased flexibility.
  17B4: 17.33mm, .682 inch cup diameter; 26 throat. Well suited for the player looking for a shallower cup in a larger diameter. Medium-small B cup offers more brilliance for projection with number 4 semi-flat rim for comfort.
  17: 17.33mm, .682 inch cup diameter; 26 throat. A compromise of all the medium characteristics, this mouthpiece is an excellent medium to large diameter mouthpiece.
  17D4: 17.33mm, .682 inch cup diameter; 26 throat. This mouthpiece includes a deeper D cup and number 4 semi-flat rim for improved endurance.
  17D4d: 17.33mm, .682 inch cup diameter; 26 throat. A larger blowing mouthpiece than the 17D4 because of the increase d-backbore.
  18B4: 17.52mm, .690 inch cup diameter; 26 throat. Ideal for a classical player looking for a commercial sound, the medium shallow cup and semi-flat rim provide resistance and comfort for upper register playing. Cup shape offers some sparkle in the sound with enough volume for tone.
  18: 17.52mm, .690 inch cup diameter; 26 throat. The high point being nearer to the center makes this mouthpiece feel smaller than it is. The standard characteristics produce a rich, brilliant tone.
  18C3d: 17.52mm, .690 inch cup diameter; 26 throat. Similar in dimension to the model 18 but with a larger d-backbore producing a large, teutonic tone.
  19: 17.65mm, .695 inch cup diameter; 26 throat. The C cup, number 3 rim and standard c-backbore are similar to the model 20 but with a slightly smaller diameter. 
  20: 17.78 mm, .700 inch cup diameter; 26 throat. This large diameter is for the robust embouchure. Original mouthpiece of choice for Renold O. Schilke.
  20D2d: 17.73mm, .698 inch cup diameter; 26 throat. Similar to the model 20 in diameter but includes a larger D style cup, number 2 semi-round rim and larger d-backbore.
  22: 18.03mm, .710 inch cup diameter; 26 throat. Similar to the model 20 but with a larger inside diameter.
  24: 18.29mm, .720 inch cup diameter; 26 throat. Our largest cup diameter offered. This mouthpiece provides a huge volume of sound.