This mouthpiece has the same rim as our B1-3D S5 and B1-3 S5 sizes, but with a shallower cup.  It’s only slightly shallower than a conventional C cup depth, so most people do not have an issues bottoming out with it.  It’s an excellent pops, commercial or lead mouthpiece for players who like the B1-3 series rim, and much like the B1-1LD S1, can be an all-around mouthpiece for players who have a naturally dark sound, or who prefer to play with a slightly brighter sound quality.