Flex by driver head speed: two manufacturer charts
| Flex | Callaway | Graphite Design |
|---|---|---|
| Ladies / L | Under 75 mph | — |
| Light / Senior (A, R2) | 75–85 mph | 71–85 mph |
| Regular (R) | 85–95 mph | 86–95 mph |
| Stiff (S) | 95–105 mph | 96–105 mph |
| X-Stiff (X) | 105+ mph | 105+ mph |
| Price | Check Price |
Callaway Driver Fitting Protocol [1]; Graphite Design fitting guide [2]. The two charts agree within a mile an hour or so. Flex is not standard across brands, so one company's Stiff can play like another's Regular.
What flex and weight the pros use
From the driver shafts listed in our Tour Bag Index (39 players):
| Flex | Players |
|---|---|
| X | 18 (46%) |
| TX | 15 (38%) |
| S | 4 (10%) |
| F5 (UST scale) | 1 (3%) |
| M5 (Accra scale) | 1 (3%) |
| Shaft weight class | Players |
|---|---|
| 50 g | 1 (3%) |
| 60 g | 26 (67%) |
| 70 g | 11 (28%) |
| 80 g | 1 (3%) |
The weight class comes from the number in the shaft name (a "Ventus Black 7 X" is a 70-gram-class shaft). Exact weights vary by flex and length. Two shafts use their maker's own flex scale and are listed as such.
Stiffer-than-usual exceptions in the index: Brian Harman (Graphite Design Tour AD IZ 5 S), Ian Poulter (Fujikura Ventus Blue 6 S), Louis Oosthuizen (Fujikura Ventus Red 6 S), Nelly Korda (Graphite Design Tour AD FI 6 S). These are all tour players, so even "S" here is not a sign of a slow swing.
Weight, length and feel
Callaway's protocol gives three rules of thumb. A lighter shaft may add head speed, and a heavier one may tighten dispersion. A shorter shaft may help consistency, and a longer one may add speed. Lighter shafts usually feel softer, and heavier ones feel stiffer. [1]
Signs your flex is wrong
- Too soft: the ball balloons, and misses go left (for a right-hander) with more spin than you expect.
- Too stiff: a low flight, a dead feel at impact, and misses that leak right.
These are tendencies, not a diagnosis. Swing faults can cause the same flights. A launch monitor session settles it.
Sources
- Callaway — Driver Fitting Protocol (flex by driver head speed; launch and spin targets)
- Graphite Design — 2025 fitting guide (flex by swing speed)