Bach 3415G 5G Trombone Mouthpiece - Large Shank Baritone/Trombone Cup Depth: Deep Cup Diameter: 25.50mm Rim Shape: Medium Wide, Semi Flat Description: Same Rim Shape And Diameter As No. 5 Small Shank Tenor Trombone. Similar Playing Characteristics To 4G With A Slightly Smaller Cup Diameter .276" Throat/429 Backbore.