BigBuzz Horn Training US Shank with Case

This is a BigBuzz American Shank for French Horn.
I purchased it from DAC and used it a few times, but I am selling it as it is no longer needed.
There are some surface stains and minor scratches, but the shank, receiver, and screw mechanism are in good working order.
A leather case is included.

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The revolutionary training tool [Horn BigBuzz] developed by Professor Will Sanders (Karlsruhe University of Music).
Big Buzz allows you to adjust the hole size to your preference. The larger the hole, the more air escapes, making it harder to produce a sound on the instrument, allowing you to practice with more air support.
After practicing with the hole open, remove the Big Buzz and play the horn as usual...
You will be surprised by the increased resonance and natural playing.