This is a standard mouthpiece for piccolo trumpets. The catalog size is an inner diameter of 16.68mm, equivalent to a Bach 3C or a Schilke 14. The inner rim diameter is slightly smaller than a Bach 3C. The rim is flat and thick. The outer rim diameter feels slightly larger than a Bach 3C. The rim is also semi-flat, so the edge is gentler than a Bach 3C, making it less likely to hurt even with hard pressure. The cup is shallow, about the same as a Bach E cup. The throat is 3.65mm. The backbore is about the same as a Warburton 9. This mouthpiece produces a thick sound in the mid and low registers, and a brilliant sound in the high register, making it easy to control. Please feel free to ask if you have any questions.