Bach small shank mouthpiece for trombone. Universally adopted, recommended by many music teachers, this mouthpiece is suitable for both beginners and the most demanding musiciansRimWide: Increases endurance.Narrow: Improves flexibility, range.Round: Improves comfort.Sharp: Increases brilliance, precision of attack. CupLarge: Increases volume, control.Small: Relieves fatigue, weakness.Deep: Darkens tone, especially in low register.Shallow: Brightens tone, improvesresponse, especially in high register. ThroatLarge: Increases blowing freedom,volume, tone; sharpens highregister (largest sizes also sharpenlow register).Small: Increases resistance, endurance,brilliance; flattens high register.