Used this adapter to play a Stradivarius Bach trumpet with a 1-1/2C Bach flugelhorn mouthpiece, to achieve a warmer flugelhorn-style sound.
The final lenght of the mouthpiece (mouthpiece + adapter) is far too long compared to a standard trumpet mouthpiece and so the pitch will fall down. Also it will feel very unbalanced and the wind flow will be terribly influenced by this, it will be very hard not to crack any note, unless you use a very small amount of air and really slow wind.
It won't damage a trumpet pipe and will fit well, also the mouthpiece will fit well in the adapter.
Maybe with other gear will do just fine, but with my Bb Stradivarius New York and 1-1/2 C FL mouthpiece worked terribly and i couldn't use it like a wanted.