Thank you for viewing. This is a JK (Yacht Car) 1DM horn mouthpiece. It has an inner diameter of 18mm and a throat diameter of 4.2mm. I bought it, but it felt larger than the catalog specifications to me personally, and I didn't think it suited me, so I'm selling it. Since it has been used, there are scratches on the shank, and there are also other marks (scratches?) from being stored in a case (see photo 5). There is no effect on use. I will hand it over in a clean condition, but it has been in someone's hands. To ensure a good transaction for both of us, please understand that we cannot accept claims or refunds after purchase.