curiosity about Differences in Hirsbrunner models.

[SCHSGetzen]

What are the difference in the different 4/4 sized Hirsbrunner CC tubas, beyond the obvious physical differences. (I'm thinking of the HP21, HP2, and HP2P right now)

[eupher61]

The physical differences are the differences, aside from the model name.
If you are only looking at number of valves etc you aren't looking at enough information.