This is the Yamamoto Koichiro Model 3XD mouthpiece for ultimate brass large-bore tenor trombones. I've used this with affection as my main mouthpiece for several years in orchestras and solo performances, but I'm selling it due to a size change. * The inner diameter is the same as a 2G, but the feel of the mouthpiece is closer to a 3G+. * It's the deepest model in the Yamatenor 3 series, but it's not too deep compared to other American mouthpieces, and it can handle extremely high notes. It has a 3GM feel. * It has a solid weight, so it gives a sense of security that it will support you firmly. Recommended for: * American players who are confident in their physical strength and want to blow powerfully on a tenor trombone. * Players who usually play 2nd tenor and occasionally switch to bass trombone. * As a mouthpiece option for those who usually play bass trombone and switch to tenor. * Those who play bass trombone but want to change the sound to a lighter direction by only changing the mouthpiece, such as in a small orchestra. ※ This is considerably larger than the general size for tenor trombones, so it is not recommended for small people.