Model Number: HR-IDE2 Shiro Ide Signature Model Inner Diameter: 17.81mm Throat Diameter: 4.09mm Cup Shape: U-cup Shank: American Purchased about 2 years ago. Not used very much. Although the cup diameter is large numerically, the rim is thin, so personally, I didn't feel a significant difference from a 17.5mm Schilke 8, for example. There are scratches on the shank from attaching it to an instrument. Will ship in the original box.