Originally Posted by Rookie Solara

I am not so sure about that....lets say MT 12 Mugen engine (also from Nova Rossi) their buttons are thinner then the current Nova Rossi model....at least, I cannot use the MT-12 turbo or non-turbo button onto my Mugen X12 engine UNLESS I am using the MT-12 head..........otherwise, the button will go up and down underneath the X12 engine head.

Only certain model of Nova Rossi button can match with some RB and Mugen engine, not all of them are compatable even thought they are all from Nova Rossi.