This is a set of an AR Resonance MD top and a 9 backbore with a 40 throat, which is no longer produced. It weighs 123g, slightly heavier than the Monette STC-1's 117g. It fits perfectly with Bach Yamaha, and I have also used it with Kanstul and vintage Martins. It may not fit in receivers like XO or CONN VintageOne as it is too loose. The maker mentioned that the L is almost a 10 backbore, so I think the combination of a slightly tighter backbore than the current L and a slightly shallower mouthpiece creates a very good balance. However, compared to a normal mouthpiece, it has a very open backbore, but it is easier to transition to than the Monette Prana, and thanks to the blank, it feels supportive, so it is also recommended for those who found L too tight. Also, it is incredibly easy to produce a subtone. The screw is compatible with Warburton, as with the normal model, so you can play around with it. I own many pieces from the brand's early days to the present and have never experienced compatibility issues. The plating also improved around this era, so I can confidently recommend it. The condition is good as I have swabbed it after every use. I currently use a lighter model with almost the same setting, but I am selling this mouthpiece because I have sold the heavy instrument I used it with and it is used less frequently. Reference Price Standard blank brass top + standard blank brass backbore back: 46,640 (tax included)