Standard 51D upperworks with a number 1 "British" or "European" shank. Fits all older British & European models (including Besson, Willson, some Hirschbrunner and pre-1974 Boosey & Hawkes) with "medium" or "British" sized receivers. The shank on this mouthpiece is larger than traditional "small bore" and smaller than "large bore" trombone models.
Features
• 25.55mm cup diameter.
• J throat
• Medium-deep "D" cup
• Standard rim
• Standard backbore
• European/British shank
• Silver plated