Features The Bach 5GS Small Shank Trombone/Euphonium Mouthpiece is made for players with good, natural embouchures. It features a rather large cup, and helps produce a full, mellow, sonorous tone. Also has the larger “G” throat and #420 backbore backbore compared to the 5 Mouthpiece Cup Depth: Medium Approximate Cup Diameter: 25.50 mm Rim Shape: Medium Wide, Semi-Flat Model:3505GS Manufacturer:Bach