Few companies know more about mouthpiece manufacture, design and physics than the Schilke Company. They make a complete line of excellent trumpet mouthpieces that work with any instrument but especially compliment their fine line of outstanding trumpets.Cup Diameter (First number in label): cups range from shallow to deep in numeric order from low to highCup Volume (First letter in label): volume ranges from A to E from small to large - A: Small; B: Medium-Small; C: Medium (Standard); D: Medium-Large; E: LargeRim Contour (Second number in label): rims range from roundest to slightly rounded in numeric order from low to high - 1: Roundest; 2: Simi-Round; 3: Standard; 4: Semi-Flat; 5: Slightly RoundedBackbore (Last letter in label): backbores range from tight to large in alphabetical order: a: Tight; b: Straight; c: Standard; d: Slightly Curved Out; e: Large