Vincent Bach 5GS Trombone Mouthpiece Large Shank (Bach 341-5GS)Vincent Bach 5GS Large Shank Trombone Mouthpiece The Bach 5GS is a variation of the standard 5G, designed with a shallower G style cup, a larger . 261 G throat, and a #420 backbore. This setup produces a freer, more open blow than the 5G while still retaining warmth and core in the sound. The #420 backbore, known for its darker tonal character, adds richness and breadth to the overall response. With a 25. 50 mm medium cup and medium wide, semi flat