The L-B4L rim is semi-round, very soft, and fairly wide. There is some undercut for chop room. The cup is medium to medium shallow, with a rounded entrance to the throat that is very receptive to good air flow. The rim and cup were designed to have a cushioned feel while making the upper register easier and livlier. The throat is a #27, the throat cylinder length is enhanced, and the backbore is a Legends S. Slotting is excellent with the L-B4L, and intonation is spot on all the way up. The design elements of this model maximize endurance and range for the player, and work together to allow a big sound in any register. Because the inside rim diameter is not extremely small (.664″), but the cup shape and depth are geared toward the upper register, this mouthpiece is very versatile. It is popular both with full-time lead players, and also with symphonic players who occasionally need a more shallow lead mouthpiece. Use the L-B4L when you want to play both technical legit music and screaming lead!