Finding the right mouthpiece is a tough ask for a brass-bander who doesn't like the feel of Denis Wick's rims (far too sharp a bite)... As the de-facto standard the Denis Wick (no-letter) sound is what one must aim to find, but alternatives that can blend with it are not easily found.
Yamaha's 16E is a good alternative, but the rim can again feel sharp.
Warburton's BC top comes close and has a supremely comfortable rim, but feels "tight" due to the narrow throat and producing the volume required is quite an ask (possible, but harder work than it need be).
GR's #7 (also known for being Sparx no letter) cup comes up rather bright and can be difficult to blend. The rim is much better than the wick but it's not quite there.
The quest ends with Marcinkiewicz 5XW - the sound is still a touch brighter than the wick (though not GR/Sparx bright) and can be brightened easily when required for soloistic purposes. For my personal playing style and tone, its projection and slightly clearer tone make it an excellent soloist/principal-cornet mouthpiece.
It's fantastically responsive and clean articulation is a breeze. The rim is very comfortable and it blows freely (and loudly, when required).
All in all, enough to stop me looking... thankfully.
(PS: The current picture shown on Thomann depicts a long-shanked mouthpiece, the 5XW is firmly in the short-shank category)
