Hammond Design Trombone Mouthpiece 13ML Rim & Inner Gold Plated Rim Diameter: 25.4mm Throat Diameter: Approximately 7.1mm Rim: Semi-flat Cup: Deep According to the Hammond Design website, this is equivalent to a Bach 6 1/2AL or a Schilke 50. My personal impression is that it's somewhere in between a 6 1/2AL and a 5GS. It's compact, but doesn't feel narrow, and has a bright tone with a wide dynamic range that's easy to control. New Price: 37,400 yen (Silver Plated) Plus gold plating, which brings the total cost close to 50,000 yen.