This mouthpiece is very well balanced. I work with a lot of bass trombonists, so I'm quite sensitive to the needs of you guys. While we all love big bass trombone sounds, a bomastic low register usually equates to a wide-open, "false ringing" upper register. This piece addresses that with a big bass sound in the low register that also works great in the upper register. And it does that without being overly bright.
Now for the specs. This GP model has a 28.58mm cup diameter and a wide overall rim diameter. That's a bit wider than a traditional Bach-like blank (1.555"). It's not uber-wide, but it does allow for more contact than most bass mouthpieces. You'll recognize the blank design as being the same as those from the Alessi line.
• 28.58mm (1.125 inch) cup diameter.
• 7.77mm (0.306") throat
• Wide 5.965mm (0.235 inch) rim width