A simple explanation of Shaft Fitting Fitting a shaft for a golfer is not as simple as knowing the right flex. A regular flex from one shaft company might well be a stiff flex with another shaft company and with yet another shaft company that same shaft might be designated as a Senior flex. Yet it is the same shaft engineering. For this reason alone you can't depend on Flex markings on the shaft when fitting a shaft.
Professional Club Fitters fit for swing speed, which measured in cpm at two points where your hands are on the grip and at the very butt of the shaft. We also fit for transition time and load, and this is measured in 3 places in the center of the shaft to give you the proper stiffness in the center of the shaft for when you start your downswing. Thirdly, we fit your wrist cock release point prior to impact, which is measured at two places on the bottom of the shaft nearest the tip. If all three sections are fitted properly the shaft should feel very good when you swing it and it should be in the best configuration thoughout your swing to give you maximum club head speed and ball speed. By fitting properly you should be more consistent and more accurate as well as hitting the ball as far as possible with your swing.
Flex marking on the shaft alone means very little in proper shaft fitting with fitting the remainder of the shaft too. Proressional Club fitters and Club Builders use frequency measurements in "cycles per minute" or cPM to measure flex along 7 designated points on a driver shaft to fit a shaft that works best for your particular swing. Let me attempt to put this into a practical golf fitting story you as a golfer can easily understand by using two golfers to explain how two totally different physical specimens can swing the same R FLEX but have two completely different shafts in feel and performance. I have one golfer (1) who is 5'8" tall
I have a another golfer (2) who is 6'5" tall
1 has a fused spine and cannot turn
2 is as limber as can be and has a big turn as a result, you might expect...
1 has a short quick swing
2 has a long fluid swing
1 complete swing takes only .9, (or 9/10ths of a) second
2 complete swing is 1.2 seconds to long, or 25% longer than 1
The end of 1's backswing is at 9 o'clock or waist high
The end of 2's backswing is at 12 o'clock or on top of his head
1 releases his wrist cock at 7 o'clock
2 releases his wrist cock at 10 o'clock
1 & 2 both have a clubhead speed of 90 mph
1 & 2 use shafts from the same company with the same R flex as you would expect But, that is where the similarities end...
1 has a stiff mid section in his shaft to control his abrupt transition that puts a load on the shaft
2 has a soft mid section because he does not load the shaft at all because his swing is so smooth you can hardly tell where his back swing ends and his downswing begins
1 has a very stiff tip section because of his late release
2 has a very soft tip section because of his early release
1 can't hit 2's driver without feeling like he is out of control and he has to swing very soft so he don't loose it, and 2 says 1's driver is too stiff and boardy feeling for him and feels line an extra stiff shaft and it’s too heavy too.
Although both have an R flex, they have two entirely different shafts in spite of the shafts being made by the same company. This is why we do fittings, to test golfers for these and other swing characteristics that will influence how we need to build your golf clubs. We use launch monitors and video cameras to record the information about your swing so we can analyze it and build the club that fits your swing best. | 
