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Hi, I would like to ask informations about Bach small shank (without letter). What is cup depth on Bach 4? Kind of 6 1/2 A depth ? How is it rim contour? Flat or round? Thank you for your answer

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https://mouthpieceexpress.com/media/bach/bachmouth.pdf

Bach 4 | Medium depth cup | 26.00 mm cup I.D. | Medium wide rim, well-rounded | Very large cup; principally used by players having healthy, strong embouchures.

Larger cup than a 6½AL, but much smaller throat (5.85mm for 4, vs. 6.63mm for 6½AL 

I found the no-letter pieces to be a bit restricting.

Posaunus wrote: Fri Feb 06, 2026 2:35 pm
Larger cup than a 6½AL, but much smaller throat (5.85mm for 4, vs. 6.63mm for 6½AL 

He asked for a 6 1/2 A which have a 5,85 throat.
The A cup is deeper then 4 cup. All no letter Bach mouthpieces have a B cup.

heinzgries wrote: Fri Feb 06, 2026 3:40 pm

Posaunus wrote: Fri Feb 06, 2026 2:35 pm
Larger cup than a 6½AL, but much smaller throat (5.85mm for 4, vs. 6.63mm for 6½AL 

He asked for a 6 1/2 A which have a 5,85 throat

Sorry - I mis-read the original post. 6½A has the same cup as 6½AL, but much smaller throat as noted. I think the Bach 4 cup depth may be about as deep as the smaller-diameter 6½AL cup, but not sure - I gave away my Bach 4 long ago because I found it to be unbalanced.

Thank you for the answers. I already read specs on catalogue, but I wanted to know yours real thoughts about. So, we can say it is essentially Bach 6 1/2 A with bigger rim (4G size) , rounded like 6 1/2?