The B1-3 S5 is a great orchestral mouthpiece with a huge sound and a cup similar to the conventional C cup depth.  The inside rim contour is rounded, but the outside edge has a medium contour.  It is comfortable on the chops without too much “bite,” but the rim feels a little wider and less rounded than the B1-1 series.  This mouthpiece is popular with 1C player who prefer a slightly more rounded rim with a little less bite.