This is a set of WHF F-tuba mouthpieces, including a heavy cup and a light cup. The rim is JW6, the cups are S6 (heavy & light), and the shaft is W6. The size 6 model has an inner diameter of 32.0mm. I purchased these after trying them out, but I don't think I'll be using them, so I'm putting them up for sale. There are no noticeable scratches or dents. Since both heavy and light cups are included, you can express a variety of tones. My impression is that they are not as heavy as they look, and they respond quickly, producing a uniform sound across the entire range of the instrument.