I've played a lot of Zinner bass sax mouthpieces because Benedikt Eppelsheim was good enough to exchange pieces with me until I found what suits me best. Most of the Zinners were very good. There are four chambers:
A chamber - Large chamber with a tiny rollover baffle just behind the tip, close to the old Conn bass mouthpieces, but a little louder and brighter, with a larger selection of tip openings. My favorite, especially when you don't have to blow the walls down.
B chamber - Medium chamber, meaning the chamber is the same diameter as the backbore. However, the backbore for Eppelsheim and Keilwerth basses is enormous, so the chamber is still pretty large. There is a rollover baffle that extends about 3/4" back from the tip. It looks a lot like an old slant signature baritone sax mouthpiece, and it performs in a similar manner on bass sax. It's a lot louder and brighter than the A chamber, but still manageable. The "bad" notes on vintage basses, such as C natural with the standard fingering, are still pretty good with this mouthpiece.
C chamber - A lot like the B chamber, but the rollover baffle is much higher. The chamber in back is still fairly large. I would describe the sound as "brittle" and this piece is much less flexible.
The standard Keilwerth Zinner has a square chamber much like many modern high baffle mouthpieces. I use square high baffles on tenor and baritone, but I can't see any advantage of this Zinner piece over the B chamber. I'm sorry, but I forgot the designation of this chamber.
As far as tip openings on the Zinners. By actual measurement of my own Zinner bass pieces, using a very accurate Theo Wanne tip gauge, the openings are:
Zinner bass sax 6 = .095"
Zinner bass sax 7 = .100"
Zinner bass sax 8 = . 108"
Zinner bass sax 9 = .120"
There are also 2 backbores. The big one, for Eppelsheims and Keilwerths (Coufs, also) has a backbore of about 20 mm. Not a bad thing, really, because you can recork an old Conn or Buescher neck with standard 1/16" cork like a tenor sax and it fits.
However, if you intend to swap back and forth between the Zinner and a baritone sax mouthpiece, I understand Zinner makes these mouthpieces with a smaller, baritone sax sized backbore. I have never seen one of these, though.
A chamber - Large chamber with a tiny rollover baffle just behind the tip, close to the old Conn bass mouthpieces, but a little louder and brighter, with a larger selection of tip openings. My favorite, especially when you don't have to blow the walls down.
B chamber - Medium chamber, meaning the chamber is the same diameter as the backbore. However, the backbore for Eppelsheim and Keilwerth basses is enormous, so the chamber is still pretty large. There is a rollover baffle that extends about 3/4" back from the tip. It looks a lot like an old slant signature baritone sax mouthpiece, and it performs in a similar manner on bass sax. It's a lot louder and brighter than the A chamber, but still manageable. The "bad" notes on vintage basses, such as C natural with the standard fingering, are still pretty good with this mouthpiece.
C chamber - A lot like the B chamber, but the rollover baffle is much higher. The chamber in back is still fairly large. I would describe the sound as "brittle" and this piece is much less flexible.
The standard Keilwerth Zinner has a square chamber much like many modern high baffle mouthpieces. I use square high baffles on tenor and baritone, but I can't see any advantage of this Zinner piece over the B chamber. I'm sorry, but I forgot the designation of this chamber.
As far as tip openings on the Zinners. By actual measurement of my own Zinner bass pieces, using a very accurate Theo Wanne tip gauge, the openings are:
Zinner bass sax 6 = .095"
Zinner bass sax 7 = .100"
Zinner bass sax 8 = . 108"
Zinner bass sax 9 = .120"
There are also 2 backbores. The big one, for Eppelsheims and Keilwerths (Coufs, also) has a backbore of about 20 mm. Not a bad thing, really, because you can recork an old Conn or Buescher neck with standard 1/16" cork like a tenor sax and it fits.
However, if you intend to swap back and forth between the Zinner and a baritone sax mouthpiece, I understand Zinner makes these mouthpieces with a smaller, baritone sax sized backbore. I have never seen one of these, though.