I wanted a loud mouthpiece for the occasional over-the-top volume gig. I bought an M2 Plus 110 and was disappointed with the small tip - I normally play a brass M2 120. Sent it to Keith and described it as "tip too small, not enough resistance". (I like when a mouthpiece pushes back). I also sent him one of my M2 120's for comparison. I knew he could open the tip, but I assumed adding resistance, a la offset SMS Berg, was out of the question. He opened it to a 125 and succeeded at adding resistance right where I wanted it. The mouthpiece is scary and turned my nickel SX90R into a nuclear weapon. The guy's a master.