For years musicians have asked us for a mouthpiece between a B2 and a B3 in size with a comfortable rim, a huge sound, and an extra quick response. 
 
The rim is slightly flatter and has a bit more of a cushion contour than the B3S3 or B2S3, with an inside diameter falling between the two sizes. The cup depth is slightly shallower than a standard “C” cup.  The unique cup shape provides a very large cup volume for its depth, which helps the player produce a remarkably full sound for a mouthpiece of this size. The shape of the cup also provides help in the upper register.  This mouthpiece is popular as an all-around mouthpiece, especially for people play in many different situations (big band sections, pit orchestras, wind ensemble, etc), and want to use one mouthpiece for everything.  Many 3C or 1 1/2C players who would like a more brilliant sound and easier upper register love the B3F S7.