4B Classic series Trumpet Mouthpiece. SThis mouthpiece was originally based on the Vincent Bach 7C, one of the most popular trumpet mouthpieces in the world. The 4B has a medium depth U-shaped cup and a medium-large bore. The inner edge of the rim was designed to be a little less sharp than the Bach version, giving greater flexibility and a more comfortable playing experience. The 4B works equally well on B♭, C and D trumpets, and is the perfect size for beginners and intermediate players. It produces a solid and bright sound, and is one of our best-selling trumpet mouthpieces. Specifications: Cup diameter: 16.50 mm, Rim width: 5.18 mm, Throat: 3.7 mm, Backbore: Barrel. Finish: Silver plated