On a golf club shaft flex chart, each letter corresponds to the stiffness of the flex. You'll find five commonly used shaft flex ratings: X for extra stiff, S for stiff, R for regular, A for senior and L for ladies.
Shaft flex impacts your swing in a variety of ways, so reading the flexes correctly can help you select the right clubs to improve your game. Generally, the faster your swing speed, the stiffer the flex you will need in order to keep the clubface aligned at impact.
Most golfers don't have access to swing speed measuring tools, such as radar. You can use your driver carrying distance as a general guideline. If you can carry the ball over 250 yards, choose stiff flex. For more than 230 yards but less than 250 yards, choose regular. For over 200 yards but less than 230, choose senior flex. Anything less than 200 yards, choose ladies. Extra stiff is rarely used by casual golfers and is typically reserved for only the biggest of hitters, such as professional golfers.
The best way to get the right flex for your clubs is to have a professional fitting. The fitter gauges not only the speed, but the tempo of your swing, helping to match the flex to your game.