This mouthpiece is similar to the 1B size, and is a popular mouthpiece for classical and orchestral playing.  The B1-2D S3 has a flatter rim contour than our other 1 series mouthpieces, and a fairly sharp bite on the inner edge.  Our clients who played the original B1-2 and find the new B1-2 S3 a little too shallow or bright usually love the B1-2D S3.  Also, players who like the feel of the old Bach 1 rim and cup size usually love the B1-2D S3 size.