Flex is at best a relative term. Within one shaft line, X to A/L flexes will have an increase in torque to account for a decreasing transition change of direction. Between different lines of shafts, there is no performance measure to compare one R flex to another R flex. The number of available shafts and how they flex based on mid shaft and tip shaft bend points is mind boggling even before including the flex options for each shaft line. These points impact selection if the shaft needs to launch higher lower than your current. Even graphite to steel has overlapping models - graphite is not just for the elderly. A good fitter will have a general idea of which shaft models would likely be the best starting points based on observing/measuring your swing and interviewing you what you know about your current setup. Launch angle and overall shaft weight would be key here. Then fine-tuning the flexes in that shaft model. Reading the custom options available online from Titleist even just for irons is way too much information.

The simplest solution is to find a Titleist Thursday or a pro that is willing to spend an hour or so working with you and explaining all the decision points in arriving at the final selection.

Fitting is the key, and just like in the cycling industry, lighter stronger materials are all about making the game fun. I just got fitted for the AP3s, and the result of each shaft option was all the proof I needed. My recommendation to anyone considering new clubs is to get fit, you won't be dissappointed.