Vincent Bach was a rare combination of artist and engineer. He constantly changed his mouthpieces in search of the perfect design. It wasn t until the mid 1960 s that he stopped and finally settled on more standardized design. This created the standard for mouthpiece making that is still used today. These standards are now known as the Classic Series. Bach Classic Mouthpieces are the most played mouthpieces in the world by students amateurs and professionals! Bach Standard Trombone Mouthpiece Small Shank Silver Plated 8.5BW. Cup Size 8BW Cup Depth Medium Shallow Cup diameter 24.75mm Rim Shape Very Wide Well Rounded.