310-M 9 cup inner diameter 32mm throat 7.8mm There is a dent on the outer circumference of the rim, but it does not affect the performance. I am selling it at a low price because of this, so please understand. A classic mouthpiece for F tuba from the old days. For those who are desperately looking for an old 64, why not give it a try? (My personal opinion) It's a very good mouthpiece, but I'm selling it because I changed instruments. tilz, bruno tilz, pt-64, tuba, euphonium, mouthpiece