Same size as No. 11 but with a medium shallow cup for a brilliant ringing tone of large volume. Bach trumpet, cornet and flugelhorn mouthpieces have been numbered in an orderly progression from the largest to the smallest diameters and from the deepest to the most shallow cup, each with a choice of rim designs.Model numbers progress numerically from model #1 with the largest cup diameter, to model #20C with the smallest cup diameter. Cup depths are notated with letters. #A# cups are the deepest; standard cups have no letter designation; progressively shallower cups are marked B to F.
24.70 mm medium shallow cup. Medium wide rim