26 September 2026 · 7 min read
Regular, stiff or senior: reading flex off your own speed
Regular or stiff is the wrong question. The right one is how fast you swing and what the ball does.
Regular or stiff is the most common question when buying a club and the worst posed. It assumes the letters mean something fixed. They mean nothing fixed, and you can see that in any manufacturer's price list.
Three shafts are called stiff
The stock selection for a single driver contains several shafts all called stiff, weighing 55, 61 and 66 grams (PING). On top of that come shafts that use no letters at all: Project X counts 5.5, 6.0 and 6.5, and one lightweight shaft is called 35 or 45.
| Shaft | Flex designation | Weight |
|---|---|---|
| ALTA CB Blue 50 | Soft Regular | 49 g |
| ALTA CB Blue 50 | Regular | 51 g |
| ALTA CB Blue 50 | Stiff | 55 g |
| Tour 2.0 Chrome 65 | Regular | 56 g |
| Tour 2.0 Chrome 65 | Stiff | 61 g |
| Tour 2.0 Chrome 65 | X-Stiff | 66 g |
| Project X Denali Red 60 | 5.5 | 56 g |
| Project X Denali Red 60 | 6.5 | 58 g |
| ALTA Quick | 35 | 38 g |
| ALTA Quick | 45 | 45 g |
There is therefore no standard against which a flex could be measured, and no manufacturer obliged to follow anyone else's. A stiff from brand A can be softer than a regular from brand B. Buy a club by the letter and you are buying a label.
What stiffness actually does
The shaft bends back during the downswing and kicks forward shortly before impact. That movement helps determine how much loft the face really has at impact and where it points. A shaft too soft for your speed comes forward too early; one too stiff does not come forward at all.
The classic symptoms follow from that. Too soft means a high launch, plenty of spin and a ball that pulls left. Too stiff means a flat launch, little feel and a ball that stays right. Both are described for a right-hander and mirrored for a left-hander.
The number it hangs on
Club head speed. TrackMan uses 94 mph with the driver as its standard assumption for an average golfer (TrackMan); the PGA Tour swings 115, the LPGA Tour 96. A woman off handicap 15 is around 79 mph.
That number is the first pointer, not the answer. It tells the fitter which range to search; which shaft in that range fits is decided by ball flight. The table by handicap and how to measure are in Club head speed.
The tempo factor nobody mentions
Two players with the same speed need different shafts if their rhythm differs. True Temper names tempo explicitly as a fitting criterion: not how fast somebody swings, but how they swing it fast. A jerky transition from the top loads the shaft more than a smooth one.
So an aggressive swing at 90 mph often suits a stiffer shaft than an even one at 95. That is why a table alone is never enough, and why two players off the same handicap play different shafts.
Senior and ladies are weights, not ages
Behind the designations A or senior and L or ladies stand the softest and lightest shafts in the range. At Ping they are called Soft Regular and ALTA Quick and weigh 38 to 49 grams against 66 grams for X-stiff (PING).
A man at 78 mph belongs in those shafts whatever the sticker says, and a woman at 95 mph does not. The name is marketing; the weight and the stiffness are the substance.
With irons it is the same
There too the same flex letter appears at very different weights: regular exists at 72, 93, 96, 103 and 104 grams (PING). Choosing a flex in irons really means choosing material and weight first and stiffness second.
A common mistake is carrying the driver flex over to the irons. The clubs are different lengths, swung at different speeds, with different shafts. Playing regular in the driver and stiff in the irons, or the other way round, is normal.
The test in one hour
Book a bay, take your driver and two demo drivers in neighbouring flexes, ten balls each, alternating. Write down club head speed, launch angle, spin, carry and lateral dispersion, and drop the best and worst shot of each series.
The right shaft is the one with the smallest dispersion at equal or greater carry, not the one with the single longest shot. If two are equally good, take the heavier: it holds the rhythm when you get tired.
How to test a flex without buying
Three routes, none of them binding. A demo day at the club where a manufacturer brings the fitting cart. The pro shop, which lends demo clubs for a range hour. Or a bay with rental clubs, where you hit two neighbouring flexes back to back.
In all three cases bring your own club. Without a reference point a number tells you nothing, because you do not know whether 94 mph is a lot or a little for you. Your own club is the baseline, and without it half the hour is wasted.
The shaft in your wedges
In wedges the flex hardly matters and the weight does. Most wedges come with the heaviest shaft in the set, because you rarely swing them fully and you need feel; that is why many people play steel in their wedges even with graphite irons.
The only thing that matters is not making the jump too big. A graphite 9 iron at 65 grams and a steel wedge at 130 feel like two different sets, and you notice it exactly on the shots around the green.
Shaft length belongs to the question
A shaft gets shorter with every iron: a classic steel set runs from 40.0 inches in the 3 iron to 37.0 inches in the wedge (True Temper). A longer shaft swings faster and strikes less centrally; a shorter one the other way round.
So lengthening a shaft is only a solution when your height calls for it, and never a way to gain metres. Buy used and you inherit the previous owner's length and flex at once, which is the most common case of a wrong shaft in a bag.
More on this: Golf for women in Switzerland.
When the question arises
When buying a driver, after a clear change in speed, and when an old set has been handed down. A club from your father or from the second-hand rack carries the previous owner's flex, and that is the most common case of a wrong shaft in a bag.
What a fitting costs in Switzerland and which values are recorded is in Golf fitting in Switzerland. Whether you want steel or graphite at all is settled in Steel or graphite, and a venue to measure at is on the map.
Frequently asked questions
Which flex suits which speed?
As a pointer: below about 85 mph the softest and lightest shafts, around 90 to 100 mph regular to stiff, above that stiff to X-stiff. The letters are not a standard, so ball flight decides in the end, not the table.
How do I notice my shaft is too soft?
The ball launches high, takes plenty of spin and pulls left, for a right-hander. Too stiff is the opposite: flat launch, little feel, the ball stays right. It is only certain once a launch monitor shows launch angle and spin.
Is a stiff the same at every brand?
No. There is no standard for flex. In the stock selection of a single driver, shafts of 55, 61 and 66 grams are all called stiff, and other models drop letters entirely and count 5.5, 6.0 and 6.5.
Do I need the same flex in driver and irons?
No, and it is normal for them to differ. The clubs are different lengths, swung at different speeds, with different shafts. Regular in the driver and stiff in the irons is a common combination.
What do senior or ladies flex mean?
The softest and lightest shafts in the range, at Ping 38 to 49 grams against 66 grams for X-stiff. The label says nothing about age or gender: speed decides, not the sticker.