Bass Trombone Mouthpiece Yamaha Douglas Yeo Model Custom GP Finish Model for orchestra players, combining rich volume and flexibility. Cup Inner Diameter: 28.72 Rim Contour: Slightly Flat Rim Thickness: Slightly Thin Cup Depth: Slightly Deep Throat Diameter: 8.00 Backbore: Slightly Wide Finish: Custom GP Minor scratches present. Shipped via Takkyubin Compact.