Regular vs Stiff Flex Golf Irons (What Is Senior Flex In Golf Clubs?)

When you set out on your golfing career, there are several elements of the game that will quickly become apparent about your play – your swing speed, the degree to which you need forgiveness in a club… and the degree of flex that’s shaft flex that’s right for you in your irons.

Regular vs stiff flex golf irons

We’re focusing most on three gradations of flex – Regular, Stiff, and Senior – but there are actually a few more than that.


But first thing’s first. What do we mean by shaft flex?

It’s pretty much exactly what it sounds like – the degree to which the shaft of your iron bends in response to the forces you bring to bear upon it during your swing.

There are six levels of flex commonly in use among golf club manufacturers in the amateur game, with an added extra, mostly for professionals – and in their driver:

XXS is extremely stiff – that’s the choice available to pros in their drivers. The likelihood of you needing or seeing one is small enough to make it invisible in the everyday game.

X is Extra Stiff. You’re going to need a very high swing speed to get the most of this

S is Stiff – for golfers with high swing speeds.

U stands for Uniflex, and is a flex level specifically created as a mid-step between stiff and Regular.

R is Regular – which responds best to the most common kind of swing – not overly fast, not painfully slow. Also known as regular by default, because it’s the flex level where most people’s swings would be best suited.

A or M is Senior. Wait, what? What happened to representative lettering? Think of M as standing for Mature if it helps you remember it. This is a flex level slightly softer than Regular, meaning a swing speed slightly slower than standard.

L is sexist as hell, but it stands for Ladies, being the most flexible flex available, to work well with the softest, slowest swing speed. Yes, absolutely, it needs changing. This is the 21st-century, not the 19th.

If we’re comparing a Regular shaft and a Stiff one (stop sniggering at the back, we’re all golfers here), the truth is pretty straightforward – a Stiff shaft will need more swing speed to get the most out of it.

The Regular Shaft bends more, and is suitable for golfers with a decently swift swing speed, but nothing extra-fast.

Do I need a Stiff one?

That depends. If you have a swing speed of between 90-105 mph with your driver, or if you’re a taller golfer, using longer clubs in general, you’re probably well advised to start off with a stiffer shaft on your irons.

If your driver swing speed is in the region of 85-90 mph, you’re more of a Regular flex golfer. A Regular flex will help you get maximum distance out of your irons.

You can probably get the idea that if a Stiff flex shaft is for golfers with a driver swing speed of 90-105 mph, and a Regular flex shaft is best suited to golfers with a driver swing speed of between 85-90 mph, that a Senior flex shaft will be perfectly suited to the next swing speed level down. From 75-85 mph in swing speed on your driver means you should be thinking about Senior Flex.

It’s important, when these terms get flung about, to remember they’re relics from the 19th-century. Under no circumstances do you need to be “a lady” to use Ladies flex – that’s based entirely on the notion that muscles in women were “unladylike,” and so when women took to the golf course, they were expected to have the slowest swing speed, and therefore to need the most flex.

Similarly, Senior flex is placed where it is in the hierarchy to reflect the notion of a player who had used Regular flex when they were in their prime, but had since slightly fallen off in swing speed, and so needed a little more flex to get the job done.

These are outdated ideas, and in the 21st-century, the central truth is that you should use whichever level of Flex helps you get the best result out of your iron play.

Why do different Flex levels matter?

They don’t, really – unless you want to hit straight shots, distance shots, or get the golf ball anywhere near where you think it should go.

If you find you do care about those things, you’re going to want to make sure your flex level is right.

If you have too much flex in your shaft for your particular swing speed, you’re likely to hit high hooks, because the club won’t be able to handle the speed you’re putting into it.

Likewise, if your shaft has insufficient flex, you have a lot of low slices to look forward to with ungovernable frustration, because in that case, you can’t give the club the speed it needs to hit straight.

You should be able to get fitted with the right level of shaft flex at your club. If not at the club, then certainly, you should be able to find out your swing speed at your local driving range.

How does that work?

It works through something called a flight scope test. Again, most driving ranges will have the facilities to get you pegged to a swing speed, even if your club doesn’t.

You swing your driver (or a range driver, if you have yet to buy your clubs – which may be a useful precaution until you know your swing speed), and the speed is measured any number of times.

You should find you have a range, and from that, your general driver swing speed is established, most likely somewhere on this list.

  • Below 75 mph = Ladies
  • 75 to 85 mph = Senior
  • 85 to 95 mph = Regular
  • 95 and above = Stiff

If you find yourself in the Senior flex category, and you’ve been trying to get by with a Regular, on changing down a gear, you may well find you get higher shots, giving you more distance and far greater straightness of shot.

Ultimately, the point is not to think of Stiff, Regular, and Senior flex shafts as a competition. The shafts don’t care, and they’re not there to judge you. They’re there to help you play the shots you want to play, by matching your swing speed to the flex level that’s right for you.

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