This is a tenor saxophone mouthpiece made by Eisen, a wonderful Japanese manufacturer. This SO model is based on the Selmer Soloist short shank vintage mouthpiece. The opening is 7 (2.55mm). It's very easy to play and has a warm, round tone, but it's not muffled and can produce clear articulation. Recommended for those who like a thick sound. There are some dirt and scratches, but I think the condition is not bad. I liked it, but I'm selling it because I don't use it as often. #tenorsax #mouthpiece #eisen #soloist