YAMAHA HORN MOUTHPIECES Custom Series Yamaha Horn Mouthpiece Custom Series. [32GP HR-32-GP Rim Inner Diameter 17.48mm / Throat Diameter 4.40mm] Larger rim inner diameter than 31, with a powerful sound in the low register. Large cup capacity provides a calm and rich resonance. YAMAHA HORN MOUTHPIECES Custom Series Yamaha Horn Mouthpiece Custom Series. Finished with luxurious thick pure gold plating. Flexible and smooth mouthpiece feel. Smooth airflow and fine tone. The outer cup shape is finished thinly and uniformly, adjusted to provide a rich, horn-like sound across the entire range. These have a unique inner diameter shape, ranging from a shallow U-cup to a smooth, deep V-cup, reaching a slightly wider throat diameter, and have very flexible characteristics. The cup shape is a double cup.