This is a Monette Resonance Model! The inner rim size is about a 1-1/2. The rim is flat and thick. The rim feels soft on the mouth. The outer rim size feels slightly larger than a 1-1/2. The inner rim edge is more defined than a Monette STC-1 B4S3. The inner rim edge has a slightly deeper undercut than a Monette STC-1 B4S3! The throat is about a #19 (4.21mm). The backbore is about a Warburton 8. The shank end thickness is about 0.65mm. When playing, the vibrations of the sound are transmitted to the instrument body, creating a resonant playing feel. It has a thick, rich core and produces a very full and warm sound. I think this is a versatile mouthpiece that can be used for everything from orchestras to combos!