Yamaha Horn Mouthpiece 32D4 Rim Inner Diameter: 17.48mm Bore Inner Diameter: 4.50mm ~From the HP~ The largest model with a double cup, also suitable for Wagner tuba. With a particularly large cup capacity, it has a dark and heavy sound, making it easy to play in the low register. Used a few times, but I don't think I'll use it anymore, so I'm putting it up for sale. It takes air well. Easy to play low notes.