The 52D measures 25,78mm against the 25,55mm of the 51D. The 52E2 is 25,91mm: it's a good mouthpiece but it has a narrow edge. You have to see if it fits your chops. I don't recommend the Schilke Symphony series:I tried it on the trombone in the past, but I returned to the normal 51 before switching to K&G. I, on the Besson Prestige, feel good with a much larger diameter than those used by the euphonium players of this forum: I modified a K&G, now with an internal diameter of about 28mm, with a V profile and a narrow edge: I feel it very good, both in the lower and high register ( high natural B comes out very easily), greater security in pianissimo attacks, brighter and more sonorous sound than the K&G3D,on the other hand I lost something in terms of resistance. Mouthpieces that I used and liked was: SM3, SM3X and K&G3D.
P.S.: if you want I have a Schilke 5,1D* modified for euphonium with a bigger inner diameter and a deeper cup which I don't use anymore.
Last edited by franz; 08-13-2019 at 01:31 PM.
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.