This mouthpiece was used only once at a concert after purchase. It's a Bob Reeves horn mouthpiece, known for their trumpet mouthpieces. The inner diameter is 17.5, but the rim shape is round and gently slopes outward, giving it a unique feel on the mouth. You might feel a bit of a difference if you're used to using Schilke or Tilz. Those who use McWilliam might find the transition easier. The sound is very good, and although the shank is listed as American, it fit snugly on my Alexander 103 (30,000 series) without any play. The throat is also wide, making it easy to blow into without feeling constricted. However, it's not specifically geared towards the lower register; I think it's a well-balanced mouthpiece. I looked up the retail price, but it varied depending on the seller, so I couldn't determine it. It seems to be sold for around 30,000 yen on online shopping sites. I don't think there are any scratches that affect its use. Feel free to comment if you'd like additional photos, want to check its condition, or negotiate the price. Manufacturer's Description: From Bob Reeves, a mouthpiece maker in Los Angeles, USA, with over 50 years of history, comes the long-awaited new French horn mouthpiece! This newly released French horn mouthpiece was developed in collaboration with Dylan Hart, one of the top studio players based in Los Angeles, based on the design of John Mason, widely known in America as an expert in French horns. Through a long and dedicated development process, it has already gained recognition among professional players in America as a mouthpiece that "achieves outstanding operability and a sound rich in color." Rim Inner Diameter: 17.5mm Bore Diameter: 12 ← Probably 4.8mm Shank: American Shank Finish: Silver Plated John Mason A leading freelance player in Los Angeles. He is a university lecturer and also a specialist repairman, a well-known French horn researcher in the wind instrument industry. Dylan Hart He has participated in many film soundtracks, and has played lead in major films such as "Star Wars: The Rise of Skywalker," "Star Wars: The Last Jedi," and "Jungle Cruise."