This is a mouthpiece by Charles Colin, famous for his "Advanced Lip Flexibilities" lip slur method book. He is known to have taught the young Freddie Hubbard and Lee Morgan. Randy Brecker also used mouthpieces from this maker. The size is about the same as a Bach 10 1/2. The rim is semi-flat with a normal thickness. The inner edge angle of the rim is somewhat sharp. The cup is about the same as a Bach D. The throat area just before the bore is thicker. The throat is #27 (3.66mm). The backbore is about the same as a Warburton 6. It has a good response, yet produces a rich, orthodox sound with a core. It's easy to control, with a stable pitch and focus. The sound doesn't spread out around the receiver, but rather resonates from the bell. Please feel free to ask if you have any questions.