Vincent Bach 6-1/2AM Trombone Large Shank Mouthpiece Rim Diameter: 25.40mm Cup Depth: MD Rim: MW (Moderately Wide, Rounded) Based on the 6-1/2A, this model features an F-throat and #413 backbore for a deep, resonant sound. This mouthpiece was used with a Bach 42A trombone. It is recommended for players seeking a brighter and clearer sound than the 6-1/2AL. This mouthpiece is a current model, without the "Corp." engraving. Used only 2-3 times, and is being sold because I switched to a different mouthpiece. This is a standard mouthpiece that comes with the current 42 series trombones, and is highly recommended for students and players who are new to the instrument.