Highly popular in Europe, these are three-piece mouthpieces made in Austria. I selected these two sets after extensive testing for F tuba. There are two rims: BP6 (flatter) and JW6 (rounder). There are two cups: XV6 (standard model) and SV6 (lightweight). There are two shanks: C6 and D6 (different throat sizes). You can use any combination, and each has its own interesting characteristics. Of course, you can achieve a high level of performance with any combination. Since the enjoyment of mixing and matching is the main appeal of these mouthpieces, I will sell them as a set of two.