Shaft specifications
Shaft Flex: What the Label Tells You—and What It Doesn’t
“Regular,” “Stiff,” and “Extra Stiff” identify a manufacturer’s flex designation. They do not provide a standardized stiffness measurement—or tell you how the shaft will perform for a particular golfer.
By FORJ
Source-backed educational guide. Fitting suggestions are editorial guidance, not FORJ test results or an expert-approved fitting protocol.
A player arrives with a familiar request: “I play Stiff. Keep me in Stiff.”
That is useful history. It is not yet a specification.
Before selecting the next shaft, identify the model, weight, playing length, and the player’s experience with it. The letter alone leaves too much unanswered.
The same letter does not guarantee the same stiffness
Tom Wishon’s published shaft-fitting guidance explains that the industry does not share a universal stiffness standard for flex letters.
An R-flex shaft from one company can overlap in stiffness with an S-flex from another. Different models within the same company can also differ despite carrying the same designation.
This does not make flex labels useless. It means the label needs its context.
“Stiff” is a description attached to a particular product—not a reliable cross-brand conversion.
Flex and bend profile answer different questions
A flex designation does not describe how stiffness is distributed along the shaft.
A bend profile describes that distribution: how the butt, middle, and tip sections compare in stiffness.
Two shafts sharing a flex letter can have different profiles. A single butt-frequency reading also does not describe every section. Wishon’s profiling system uses measurements at multiple positions to make those differences visible.
Where measured profile data is available, compare shafts using a consistent measurement method. Do not assume that differently generated curves or numbers are directly interchangeable.
| Information | What it contributes |
|---|---|
| Manufacturer, model, and flex | Identifies the product being discussed |
| Shaft weight | Adds a separate physical characteristic |
| Measured bend profile | Describes stiffness distribution under the stated method |
| Playing length and assembled specifications | Identifies the actual test build |
| Player results and feedback | Establishes how that build worked in the fitting |
If needed, scroll this table horizontally. Keyboard users can focus the table region and use the arrow keys.
More complete specifications improve the shortlist. They do not eliminate the need to hit shots.
Swing speed starts the search; it does not finish it
Wishon’s fitting approach considers clubhead speed alongside transition, tempo, release, and the golfer’s preferences.
Those observations help select candidates. They are not proof that every golfer with a forceful transition needs one particular shaft—or that everyone at the same speed should use the same flex.
A manufacturer’s speed recommendation can be a starting point for that model. It should not become a universal rule applied to every shaft carrying the same letter.
Test the build, not the reputation
Keep the head, setting, playing length, and other specifications as consistent as practical when investigating a shaft change. Document differences you cannot hold constant.
Then compare:
- Club speed and ball speed.
- Strike location and its variation.
- Launch, spin, and flight.
- Carry and dispersion.
- The player’s feedback about feel and effort.
A shaft that feels firmer is not automatically more accurate. One that feels easier to load is not automatically longer.
If the candidate improves the result, describe the observed improvement. Do not claim that the flex letter alone explains it.
The next test
Identify the player’s current shaft precisely. Use available specifications and measured profiles to select plausible alternatives, then compare the assembled clubs against the player’s objective.
The flex label helps identify the shaft. The fitting establishes whether it belongs in the club.
Sources & editorial note
- Wishon Golf: Changing Shafts—Should You Keep the Same Flex?
- Wishon Golf: Shaft Profiling and Comparison
- Tom Wishon: What Shaft Flex Should I Use? (GolfWRX)
Source-backed educational guide. Fitting suggestions are editorial guidance, not FORJ empirical findings or guarantees of performance.
Links identify the original publishers and do not imply their endorsement.