Thank you for viewing. This is a Werner Christoph Schmidt horn mouthpiece, size 4. I purchased it new and used it for a while, but it didn't suit me, so I'm putting it up for sale. Outer rim diameter: 27mm Inner rim diameter: 18mm Bore size: 4.5mm American shank These are the specifications. There are some signs of use on the shank due to the period of use, but there are no problems. I will clean it thoroughly before shipping, but please understand that this is a used item before purchasing. Also, please refrain from cancellations, returns, or complaints after the product has been purchased and received.