When you measure a procharger pulley (12rib) do you measure from the outer lip (widest part of pulley) or the inner lip (where the belt would actually ride)? Thank you!

Call pro charger would be your best bet.

Good point! I am just at work and can't really dilly dally on the phone with procharger...... Thought someone on here might know?

If it is the same as my pulley its to the inside where the belt sits .

Thanks Paul, this is what I assumed, but wasn't sure. Can anyone else confirm this???

Split the difference?

Confirmed.

Thank you!!!

It is measured at the root diameter of the pulley.

I had to google "root" diameter. But that makes perfect sense now. Thank you.