What the Numbers on a Shaft Actually Mean

Flex Letter: The Least Useful Number

There is no industry standard behind R, S or X. Each manufacturer sets its own bands, and the practical spread is wide enough that one company's Regular can measure stiffer than another company's Stiff in the same weight class. We have measured shafts stamped with identical letters that sat thirty CPM apart.

The letter is a marketing shorthand for a range the manufacturer chose. It is a reasonable starting shelf in a store and it is nearly worthless as a comparison tool between brands.

Butt Frequency (CPM)

A clamped shaft with a known weight on the tip is deflected and released, and the analyzer counts how many cycles per minute it oscillates. Higher CPM means stiffer. It is the single most useful shaft figure available to a fitter, precisely because it is a measurement rather than a designation.

Two caveats. First, the reading depends on clamping length and tip weight, so numbers are only comparable when taken the same way — ours are, which is why our sheets can be compared across years. Second, CPM describes overall stiffness, not where along the shaft that stiffness lives.

Read those bands as descriptive, not prescriptive. Where you belong depends on transition, not on a clubhead speed table.

Bend Profile

Two shafts can share a butt frequency and behave nothing alike, because the stiffness is distributed differently along the length. A profile describes that distribution — typically as a stiffness reading taken at several points from tip to butt.

Practically, the tip section governs how much the head lags and how the club presents at impact; the mid section governs feel through transition; the butt section governs how the shaft loads at the start of the downswing. A soft tip in a stiff butt feels entirely different from a uniform shaft at the same overall CPM.

Weight

Raw shaft weight in grams, before tipping, trimming and assembly. It is one of the few honest numbers on a spec sheet and it matters more than most golfers expect. Weight influences tempo, total club mass, and swingweight all at once, which is why we settle it early in a session and hold it while other variables get tested.

Two things to know: the finished club weighs less than the stated raw shaft weight suggests once trimming is done, and moving ten grams changes perceived stiffness even when the CPM is matched.

Torque

Torque is resistance to twisting, measured in degrees under a fixed rotational load. Lower means the shaft twists less. It is genuinely useful and it is also the specification most often oversold.

A low torque figure suits a golfer who applies force abruptly and would otherwise fight instability. It can read harsh and lifeless to a golfer with a smoother move, who may prefer a little more. Torque also correlates with weight and material, so it rarely varies independently — chasing a torque number in isolation usually means accepting a weight or profile you did not want.

Balance Point

Where the shaft's mass sits along its length. A tip-heavy shaft raises swingweight in an assembled club; a butt-heavy one lowers it. Two shafts of identical total weight can therefore produce clubs that feel three swingweight points apart, which is more than most golfers can ignore.

Balance point rarely appears on a retail spec sheet. We measure it on the rack because it explains a meaningful share of the "this one just feels better" reactions during a session.

Where to Start If You Are Self-Diagnosing

• Weight before flex. Weight sets tempo and total mass; get it wrong and no CPM saves it.
• Frequency before letter. Compare measured numbers, ignore the stamp.
• Profile before torque. Where the stiffness lives matters more than how much it twists.
• Balance point last, but do not pretend it does not exist — it explains feel.

And the honest caveat: none of this is diagnosable from a chair. Reading a spec sheet tells you what a shaft is supposed to be. A frequency analyzer tells you what it is.