The flex of a golf club refers to the “relative strength (stiffness or softness) of a club shaft,” according to PGA pro Mark Blakemore’s golf glossary. “Golf Magazine” editor Scott Kramer notes that an individual club’s flex is generally placed into one of five categories, including “regular,” designated by the letter “R.” The other categories are ladies (L), senior (A), stiff (S) and extra stiff (X). The ladies category shaft is the most flexible; the extra stiff is the least flexible. The regular category is in the middle.
Regular Flex Defined
The specifications for a regular flex shaft are determined by each manufacturer. Frank Thomas, former technical director of the United States Golf Association, notes that the golf industry lacks uniform flexibility standards. As a result, one manufacturer’s regular flex shaft may be more or less flexible than another company’s similar product. All companies agree, however, that the “regular” category sits in the middle of the five-letter flexibility spectrum.
When to Use a Regular Flex Shaft
The amount of flex in a player's shafts should be proportional to his swing tempo and speed, according to Kramer. Thomas suggests golfers with a swing speed of 80 to 95 mph typically are the best candidates for regular flex shafts. Mike Stachura of “Golf Digest,” however, says that most experienced golf club fitters “believe swing speed is only the most basic of beginnings when it comes to a proper fitting.”
Kramer’s 2006 “Golf Magazine” article cites a survey showing that just 2 percent of PGA Tour players and 10 percent of PGA Champions Tour players used regular flex shafts in their irons. He also notes that PGA Tour swing speeds average 110 mph, so the players favor a stiffer shaft to better control the club. But casual golfers, whose swing speeds tend to be lower, are more likely to benefit from a regular flex shaft. “Experts agree that most golfers play shafts too stiff for their swings primarily because they think their swing speed is faster than it really is,” Kramer said. Golf shaft manufacturer True Temper advises golfers to “use a more flexible shaft” if they wish to hit the ball farther.
Golf shaft maker Royal Precision defines frequency matching as “a highly technical method of precisely measuring and defining the flex of the golf shaft through electronic calibration." The technique is used by club fitters to provide a golfer with clubs that feature consistent flex, thereby helping golfers develop a consistent swing, according to Royal Precision.