The Sk Fiber Power Revolution has been tested by many LD club head manufacturers. Most recently, by Krank Golf. They found the spin rates were reduced on the Rage heads/Power Rev combos by about 500 rpm! compared to the Diesel shaft they have been using. no wonder you saw Lance Reader using these shafts in Texas, or, was it Shanks, I can't remember! This shaft is a popular choice among the Steel City Long Drive Team members.
The Power Revolution comes in 2 flexes: X and XX. Here are some numbers...