This model is Adam Rapa's lead mouthpiece. The rim is identical to the B4L S1 and B4LD S1, however the cup is noticeably more shallow with much more "SLAP" than the B4L S1. We have no problem recommending this model to any player who uses a B4L or B4L S1 and is looking for a mouthpiece with the same rim to provide a little more help in the upper register. This model is also now used by Ryan Kisor, lead trumpet player with the Lincoln Center Jazz Orchestra.