This is a shallow mouthpiece with a semi-round rim that is very soft and comfortable. There is some nice undercut for chop room, which makes the .636″ inside diameter feel a little larger than it actually is. The entrance to the throat is rounded to allow good air flow for a big sound, even for such a small inside diameter. Slotting is excellent with the L-MFIII. This mouthpiece was inspired by the famous MF III, but Legends Brass has added some design enhancements in the throat and backbore which enhance endurance, range and sound for the modern player. It has the Legends enhanced throat (#27), enhanced throat cylinder length, and Legends S backbore. The L-MFIII is perfect as a lead mouthpiece.