You have Club head speed of 105 what flex should you be hitting in your driver?

Swing speed is not the only thing that matters when you are getting fit for a Golf club. 105 is right on the border line for stiff/extra stiff. You should go to your local golf store, hit a few drivers and see which one is best for you.

When you have a stronger swing speed you need to think about the torque rating of the shaft (lower torque the better). Not only is the shaft flexing but the stronger you swing the more the head twists on the shaft as well. The reason the stronger players play an x-stiff shaft is because you get low torque shafts. But you can get low torque shafts in stiff as well. I would suggest for you at that swing speed a stiff flex but with a torque rating at least in the low 3 degrees. if you see a club you like look up the shaft specs online and see what the toque rating is, shafts in the 4 degrees are weak shafts, 3's pretty good, 2's or lower very good buyt also expensive.