This is a Stork CAW10 mouthpiece for French horn. It has a large cup volume, producing a voluminous sound. I don't know the detailed specifications, but the inner cup diameter is about 17.5mm, and the throat is probably in the high 4mm range. The rim is slightly flat. It has a deep V-cup. I bought it, but I couldn't play high notes properly with my embouchure, so I wasn't able to use it and it's been sitting unused. It's as clean as if it were new. A pouch is included.