Over the years I have moved on to using larger and larger mouthpieces, going from the 24,7mm of the Bach 7C when I started with the euphonium, to the current 27,7/27mm of the K&G 1D and 3D, which is the size that best suits me on the 2052 Besson Prestige. I wanted to go up the largest size of the K&G mouthpieces, the 0D, 28,5mm, but I was no able to focus the sound and was lacking in the upper register. On the trombone and baritone, however, going beyond 26mm (K&G4C) is, for me, counterproductive and, comparing it with the most trombone and baritone players, it is already a large size. I have found that a larger size of the rim allows the vibration of a larger portion of the lips and allows me a better sound quality which, however, requires a strong and trained lip musculature.
2007 Besson Prestige 2052, 3D+ K&G mouthpiece; JP373 baritone, 4B modified K&G mouthpiece; Bach 42GO trombone, T4C K&G mouthpiece; 1973 Besson New Standard 3 compensated valves, 3D+ K&G modified mouthpiece; Wessex French C tuba, 3D+ K&G modified mouthpiece.