The Kelly Screamer is of KELLY Mouthpiece lead-trumpet mouthpiece design. The rim has a remarkably cushioned feel that still provides good slotting and great note accuracy. For comparison, the diameter is near a 13a4a with the Kelly Screamer being a bit shallower. The throat is slightly tighter than a Shew-lead, and the parabolic backbore just under that of a 3E. But please - try one for yourself!
The Kelly Screamer is the most COMFORTABLE, AFFORDABLE lead-trumpet mouthpiece that you'll ever play! PERIOD!