The CR3B  has a 27 hole, and our classical back-bore. The cup has more overall volume than a 3C. We used a B cup design, but from a slightly smaller mouthpiece so that the player would not lose endurance. The mouthpiece is has a warmer sound, is quick responding, and is very comfortable. Many players have concluded that they have not lost endurance or range verses using a 3C size mouthpiece. If you're looking for a warm classical piece with a big sound that is easy to play, try this one!