The inner rim diameter is 17.68mm, and the throat diameter is 3.98mm. This is a model with a larger rim diameter than a 32C4, and its U-cup allows for playing with a contoured sound. The larger rim increases lip flexibility, resulting in richer expressiveness. Selling off as part of a stock clearance. Used for practice a few times. There are some minor scratches from use, but the overall condition is good. It has not been stored in the mouthpiece case of the instrument case to prevent scratches.