Model Number: 3CM Silver Plated Inner Diameter: 17.00mm Throat Diameter: 4.2mm Cup Shape: U-cup Shank: JK original shank Purchased about 5 years ago. The shank has been modified, so please understand and accept no claims and no returns. I used it on an instrument with an American shank, and it worked without any problems. It will be shipped in the original box.