Specifications ■ For Tenor Trombone (Large Shank) ■ Custom ■ Gold Plated ■ 51C4 ■ Rim Inner Diameter: 25.23mm ■ Throat Diameter: 6.92mm This is a trombone mouthpiece made by YAMAHA. It's a custom series with gold plating even on the inside of the mouthpiece. It has a slightly shallower cup than the 51, allowing for powerful playing. It produces a rich tone across all registers. Suitable for symphony orchestra players. Large shank. Purchased new without a box, I used it for practice about twice, but it didn't suit me, so I'm putting it up for sale. I will pack it with bubble wrap and ship it via Yamato Compact. Thank you.