Gold 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 withouta huge cup volume. A full natural sound is achieved in all registers with the balance found in the Griego Mouthpiece design. Sleek "Deco" style exterior is heavier than traditional models, allowing for a darker, more focused sound.