How to Decode the Letters On a Golf Shaft

From X-flex shafts to L-flex, decoding those letters

Golf shaft flex
All golf shafts bend in response to the forces of the golf swing. How much they bend - how flexible they are - is noted in the shaft flex rating. Chris Condon / Getty Images

Golf shafts are designated with a letter code, the letters most commonly being X, S, R, A and L. What do these letters represent? The flex - the relative stiffness - of that shaft.

What Shaft Flex Codes Mean

"L" is the most flexible shaft and "X" is the stiffest shaft:

  • "L" denotes "ladies flex"
  • "A" or "M" denotes "senior flex" (might also be designated "AM" or "A/M," or "Senior")
  • "R" denotes "regular flex"
  • "S" denotes "stiff flex" (might also be designated "Firm")
  • "X" denotes "extra stiff flex" (might also be designated "Tour")

Why is senior flex represented by an A or M? "A" originally stood for "amateur." The "M" stands for "mature" or "medium." Also, of course, "S" is taken by "stiff."

Are these ratings consistent from shaft manufacturer to manufacturer? We'll talk about that below.

Why are Different Shaft Flexes Needed?

Some golf shafts bend more than others, depending on how much stiffness is built into the shaft when it is manufactured. Shaft makers vary the amount of stiffness because golfers have different types of swings - different swing speeds, different tempos - and different amounts of stiffness in a shaft better match up to those different swings.

The slower a golfer's swing, generally speaking, the more flex he or she requires in the shafts that are in their golf clubs. And the faster the swing, the more stiffness.

Tempo also matters: A jerkier swing requires more stiffness, a smoother swing less stiffness, generally speaking.

What Swing Speeds are Associated With Which Flexes?

Knowing your swing speed and carry distance can help you select the right shaft flex for your golf clubs. These are just general guidelines, however; the best way to choose shaft flex is to go through a clubfitting.

Not every golfer can (or is willing) to do that, though.

Speed/Carry Guidelines for Driver

  • If your driver swing speed is approximately 110mph or higher, and your carry distance around 270 yards, go with X flex shafts.
  • If your speed is 95 to 110mph and your carry distance 240-270 yards, go with S flex.
  • If your speed is 85 to 95 mph and your carry distance is 200 to 240 yards, go with R flex.
  • If your speed is 75 to 85 mph and your carry distance is 180 to 200 yards, go with A flex.
  • If your speed is below 75 mph and driver distance less than 180 yards, go with L flex.

Speed/Carry Guidelines Using Your 6-Iron

Again, these are generalities ...

  • If your 6-iron swing speed is 90mph or higher and carry distance 175 yards or more, go with X flex.
  • If your speed is 80-90mph and carry 155 to 175 yards, go with S flex.
  • For 70-80mph and 130 to 155 yards, go with R flex.
  • For 60-70mph and 100 to 130 yards, go with A flex.
  • And for speeds under 60mph and carries less than 100 yards, go with L flex.

What Happens If You Choose the Wrong Flex for Your Swing?

Nothing good, my friend, nothing good! If your swing is mismatched to your golf shaft flex - if you are using an X flex shaft, for example, when you should be using an R flex shaft - you will have a harder time squaring the clubface at impact.

The way your shots are flying can clue you in to the possibility you might be using the wrong flex. See What are the effects of playing the wrong shaft flex? to learn what to watch for.

Many golfers - and this is particularly true among men - play shafts that are stiffer than they require.

Are the Flex Code Ratings Consistent Throughout the Industry?

Do the companies that make and market golf shafts all agree on how much flex makes a shaft an X, an S, and R and so on? Are there industry standards for those flex codes, in other words?

Alas, no. Golf industry veteran Tom Wishon, of Tom Wishon Golf Technologies, explains:

"Shortly after steel shafts were introduced in the 1920s, steel shaft makers discovered they could change the diameter and wall thickness of the tubes to create shafts with different amounts of stiffness to better match to the different swing speeds and strengths of golfers. Eventually, the shaft industry developed five different shaft flex designs, designated by the letters L for Ladies; A for Amateur, which evolved into the senior flex; R for Regular; S for Stiff and X for Extra Stiff.

"What is interesting is that no standard for how stiff any of the five flexes would be was ever established in the golf industry."

Today, golf companies still each have their own definitions for how much flex makes this shaft an S-flex and that one an R-flex. It's important to understand that when considering a change in equipment. Two R-flexes from two different companies are probably going to be close enough in flex that you won't notice. But it's not a guarantee, so be sure to ask questions of a salesperson or clubmaker, and, if possible, to make some swings.

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