Model Number: 2EM S.D. Stefan Dohr Model Inner Diameter: 17.5mm Throat Diameter: 4.2mm Cup Shape: U Cup Shank: JK seems to have its own unique shank, but it worked without any problems on American shank instruments. I purchased this about a year ago for 14,000 yen. I haven't used it frequently, so the cup is clean, but the shank has some scratches. Please understand and accept that this item is non-refundable and non-returnable. I will ship it in the original box.