Project X shafts

I have Ap2 712 irons & I am going to change from a S300  TT to a project X 5.5 Flighted. What shaft is correct for the heads, the tappered shaft or parallel shaft ?

 

Rocco

Try the KBS shafts too. They're 10 grams lighter and they give you 5 to 10 more yards. At a Titleist demo day, the fitter switch me from DG S300 to KBS while demoing the AP2. They were longer and felt softer. I liked them a lot. In my current clubs, I have the Project x 5.5, and like them also.