Trombone Mouthpiece for Large Bore Willie's Thein Universal II 6s PGP Equivalent to Bach 6-1/2A. Originally made for Thein, but of course, it also fits well with instruments from other manufacturers. I was using it on a euphonium. Because it's a relatively heavy mouthpiece, it's especially well-suited for those who prefer a heavy weight. It's hard to tell from the photos, but it's pink gold. Inner Rim Diameter: 25.40mm Throat Diameter: 7.14mm Manufacturer's Explanation: A medium-heavy model created in response to the requests of Peter Kerner. It fully demonstrates the potential of the Thein Universal II trombone.