Ultimate Brass Bass Trombone Mouthpiece G10 Gold Plated Finish Rim Diameter: 28.93mm / Throat: 8.08mm / Cup: Deep There are two types of G10, early and late, this is the late version. It is said to be the same specification as the later Curran Orchestral. It was discontinued due to the introduction of the Curran model, making it a rare piece.