Trombone Mouthpiece Conn 4CL GP Cup Diameter: 25.40mm (Similar to Bach 6-1/2AL) This is a signature model mouthpiece by Christian Lindberg. I purchased it used a few years ago and used it until about a year ago, but I'm currently using a different mouthpiece of a similar size, so I'm selling this one as I don't have a chance to use it. According to the official website, the suggested retail price has increased significantly in recent years. I am also listing this on other sites. The first person to purchase it, regardless of the site, will be given priority. Thank you. If you have any questions, please ask before purchasing.