Silver plated. Same cup diameter and throat size as the standard 3 (26.26mm diameter with 0.280" throat), but with less overall cup volume. The 3M (also known as the 3GM) is great for the tenor trombonist that wants the room of a larger mouthpiece without a huge cup volume. A full natural sound is achieved in all registers with the balance found in the Griego Mouthpiece design. Traditional "New York" style exterior is similar in appearance to Bach models, but slightly heavier, with the weight distributed evenly around the bottom of the cup.