Piccolo Trumpet Mouthpiece GR 65P #3. Cornet shank. This mouthpiece features a P cup with a generous volume, making it easier to maintain lip comfort, and is set up with a #3 backbore, which is standard for piccolo trumpets. Nominal Value (Size 65) Inner Diameter: 16.53mm (0.650 inch) I have many other items for sale, so please check them out if you're interested. #TPY's list of items for sale is here Type...Trumpet Accessories/Parts...Mouthpiece