91 z28 T5 with b&m ripper shifter that uses the stock knob. I want to replace the stock knob but I don't know if the one I have is (1/2-20) or (M12 x 1.25). Does anyone know what it is? If not, I will try it out at the hardware store. Btw, don't bother looking up the ripper shifter...it doesn't state what the thread is...just says to use your stock knob. Thanks in advance for any replies. Bugsy

I don't know what size the B&M shifter is; my Hurst was 3/8"-24. The stock shifter in my car was much, much larger; 16mm I think.

Well the item im looking at is the bmm billet quicksilver aluminum knob. There are two of them that look identical and both have adapters that fit 3/8-24, 3/8-16, 5/16-18 threads. But one knob is (1/2-20) and the other is (m12x1.25). I don't quite understand what that means and neither summit or jegs is able to tell me which one i need.

part #'s are bmm-80534 for the 1/2-20 and bmm-80542 for the m12 x 1.25

Mine was much larger than any of those.

Take your stock knob to the hardware or auto parts store and see what size bolt screws into it.