Mouthpiece sizes for different horns

[BrassSection]

Being the first one to admit I have a lot to learn, wondering if there is an explanation for my various mouthpieces that work. Trumpet I’m using a Bach 12B and it works fine for me. Cornet a Bach 10 1/2C works best. French horn I use a Bach 7. Daughter uses a 12 in her horn, mine came with the 7 and an 11. Tried the 11 and 12 and lose range high and low. Tenor trombone works best with Bach 12SC. Using a Bach 6 1/2 AL in euph and loving it compared to the Olds 3 that came with it or the Bach 12 I used quite awhile. Tuba using a King 26 with good results. My observation is the euph and horn a larger mouthpiece works better, while trumpet, cornet, and bone work better with smaller. Don’t play tuba often, but have the range I need with existing mouthpiece. Just wondering if this is normal, that I wouldn’t “need” smaller size mouthpieces across the board of all the various horns.

[Pezza]

6 1/2 is small for a euph.

I've found larger works better.
6.75 small tenor
5 medium & large tenor / baritone horn
3 euph
1.5 bass trom

Used a 4 on cornet, 3 on flugel, 2 on tenor horn & 2 on EEb tuba.