Activities Sports & Athletics How to Decode the Letters On a Golf Shaft Share PINTEREST Email Print Chris Condon / Getty Images Sports & Athletics Golf Basics History Gear Golf Courses Famous Golfers Golf Tournaments Baseball Basketball Bicycling Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Cricket Extreme Sports Football Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Paintball Soccer Swimming & Diving Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By Brent Kelley Brent Kelley is an award-winning sports journalist and golf expert with over 30 years in print and online journalism. our editorial process Brent Kelley Updated May 28, 2019 Golf shafts are designated with a letter code, the letters most commonly being X, S, R, A, and L. What do these letters represent? Those letters tell golfers 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." Why Different Shaft Flexes Are 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. The Swing Speeds Associated With Each Flex Rating 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 club fitting. Not every golfer can (or is willing) to do that, though. Speed/Carry Guidelines for Driver If your driver swing speed is approximately 110 mph or higher, and your carry distance around 270 yards, go with X flex shafts.If your speed is 95 to 110 mph 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 90 mph or higher and carry distance 175 yards or more, go with X flex.If your speed is 80-90 mph and carry 155 to 175 yards, go with S flex.For 70-80 mph and 130 to 155 yards, go with R flex.For 60-70 mph and 100 to 130 yards, go with A flex.And for speeds under 60 mph and carries less than 100 yards, go with L flex. Choosing the Wrong Flex for Your Swing 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 into the possibility you might be using the wrong flex. Many golfers—and this is particularly true among men—play shafts that are stiffer than they require. Flex Code Ratings Are Not 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. It's not a guarantee, so be sure to ask questions of a salesperson or clubmaker, and, if possible, to make some swings.