This mouthpiece features the same rim and cup shape as a 6-1/2A, but with a larger "G" throat (6.63mm) and a 420 (dark) backbore. It's suitable for players seeking a Teutonic (German) tone. It has a powerful yet mellow, rounded sound that projects well, making it ideal for euphonium players. I purchased this used two years ago, but it didn't suit me, so I've kept it in storage. I have many other mouthpieces for sale, so please take a look!