This is the Alliance "DC2" euphonium/tenor trombone (large shank) mouthpiece from the British mouthpiece maker, Alliance. Inner Diameter: 26.4mm Throat Diameter: 7.4mm Cup Depth: Deep This is the signature mouthpiece of David Childs, a British euphonium soloist. It's a bit large, but the rim provides a good grip, allowing for stable playing from top to bottom. I think it can produce a thick and rich sound. There are some scratches near the shank, but otherwise, it's in relatively good condition. Feel free to ask any questions in the comments!