I have my original Luyben from when I bought my first O'Brien crystal mouthpiece back in 1980(ish).
For some reason I only liked it for my crystal mpcs.
If I recall correctly when I put it on a rubber mpc I seem to lose this feeling of the reed on the mpc and want to continuously overtighten it. The plastic screw threads are very tight so you don't unscrew them much as for mine it's a PITA.
So I only use it on my crystals.
I use the BG and Vandoren and others on rubber mpcs.
For some reason I only liked it for my crystal mpcs.
If I recall correctly when I put it on a rubber mpc I seem to lose this feeling of the reed on the mpc and want to continuously overtighten it. The plastic screw threads are very tight so you don't unscrew them much as for mine it's a PITA.
So I only use it on my crystals.
I use the BG and Vandoren and others on rubber mpcs.