This is a model by Brian Hecht of Greg Go. I'm selling it because I downsized but then went back to the larger size. I'd prefer to sell them as a set, as selling them individually is too much trouble. Thank you for your understanding. Inner diameter: 27.5mm I believe the throats are different for each one, but I don't know the details. I mainly used the O, so it has the most shank wear. The A and R were only test-played, so they are almost in perfect condition.