This is an extremely wonderful mouthpiece. The sound quality, range, sound pressure, and volume are all top-notch. This is a GR mouthpiece designed and manufactured using modern technology such as acoustics. The body is engraved with the GR logo, USA, and Compu-Balanced 63S. The rim was gold-plated, but it has become quite thin. The inner diameter size is about a Bach 12. The outer rim diameter size feels like it's between a Bach 10-1/2 and 12. The cup is shallow, about a Bach E to F. The response is very good, producing a brilliant and speedy sound. You can feel the good pitch accuracy and the smooth balance across all registers. It's a design that efficiently captures the vibration of the lips within the cup, making high notes easy to control. It can handle anything from lead playing in big bands, ska, horn sections, to concert bands. It resonates well and produces volume even with a light blow, expanding the range of dynamics and expression. Trumpet Trumpet mouthpiece Trumpet mouthpiece trumpet mouthpiece