Bach mouthpieces have been designed in an orderly progression from the largest to the smallest diameters, and from the deepest to the most shallow cup, all with a choice of rim designs. Rim shape is described for each individual model. Model numbers progress numerically from model no. 1 with the largest cup diameter, to model no. 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" through "F".

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Model Approx Cup Dia.  Rim Shape

1

17.5 mm Medium thin 1X
17 mm Medium wide 1B 17 mm Medium wide 1C 17 mm Medium wide 1D 17 mm
Medium wide
1E 17 mm Medium wide 1 1/4C 17 mm Medium wide 1 1/2B 17 mm Medium wide, not too sharp 1 1/2C 17 mm Medium wide, not too sharp
2 16.5 mm Medium wide, lowered toward the outside 2C 16.5 mm Medium wide, lowered toward the outside 2 1/2C 16.4 mm Medium wide, lowered toward the outside 3
16.3 mm Medium wide 3B
16.3 mm Medium wide 3C 16.3 mm Medium wide 3CW 16.3 mm Slightly wider, lowered to outside 3D 16.3 mm Medium wide 3E 16.3 mm Medium wide 3F 16.3 mm Medium wide 5A 16.25 mm Medium wide, rounded inside edge 5B 16.25 mm Medium wide, lowered toward the outside. Medium sharp edge 5C 16.25 mm Medium wide, well rounded toward the inside and outside, fairly flat 5MV 16.25 mm Medium wide, lowered toward the outside. Medium sharp edge 5SV 16.25 mm Medium wide, lowered toward the outside. Medium sharp edge 5V 16.25 mm Medium wide, lowered toward the outside. Medium sharp edge 6 16.2 mm Medium wide, not too sharp 6B 16.2 mm Medium wide, not too sharp 6C 16.2 mm Medium wide, not too sharp, rather flat 7 16.2 mm Medium wide, lowered toward the outside. Medium sharp inside edge 7A 16.2 mm Medium wide, lowered toward the outside. Medium sharp inside edge 7B 16.2 mm Medium wide, lowered toward the outside. Medium sharp inside edge 7BW 16.2 mm Medium wide, lowered toward the outside. Medium sharp inside edge 7C 16.2 mm Medium sharp inside. Well-rounded edge with a perfect grip. 7CW 16.2 mm Slightly wider, gradually lowered toward the outside 7D 16.2 mm Medium wide, lowered toward the outside. 7DW 16.2 mm Slightly wider 7E 16.2 mm Medium wide 7EW 16.2 mm Slightly wider 8 16.2 mm Fairly wide with slightly flatter surface than No. 7. Rounded inner edge 8B 16.2 mm Fairly wide with slightly flatter surface than No. 7B. Rounded inner edge 8 1/2A 16.1 mm Medium wide with rounded inner edge 8 1/2B 16.1 mm Medium wide, lowered toward the outside. Med. sharp inside edge 8 1/2C 16.1 mm Medium wide 8 3/4 16.1 mm Medium wide, not too sharp 8 3/4C 16.1 mm Medium wide, slightly flat 9 16.05 mm Medium wide, lowered toward the outside 9A 16.05 mm Medium wide, well rounded 9B 16.05 mm Medium wide, lowered toward the outside 9D 16.05 mm Medium wide, lowered toward the outside 10 16 mm Fairly wide with rather broad, flat surface 10B 16 mm Fairly wide with rather broad, flat surface 10C 16 mm Fairly wide with rather broad, flat surface 10 1/2A 15.9 mm Medium wide, well rounded 10 1/2C 15.9 mm Medium wide 10 1/2D 15.9 mm Medium wide, high toward the inner edge 10 1/2E 15.9 mm Medium wide, high toward the inner edge 10 1/2EW 15.9 mm Extra wide, high toward the inner edge 10 3/4A 15.75 mm Medium wide, well rounded 10 3/4EW 15.75 mm Extra wide 11B 15.7 mm Medium wide, well rounded 11DW 15.7 mm Extra wide 11 1/2A 15.65 mm Medium wide, well rounded 11 3/4CW 15.6 mm Fairly wide, rather flat, not too sharp 12B 15.2 mm Broad, rather flat. 12C 15.2 mm Broad, rather flat. 17 15.1 mm Medium wide. 17C 15.1 mm Medium wide. 18C 15.1 mm Broad, rather flat.