One factor of selecting golf club shafts that is specified by the manufacturer is the flex of the club. If you try to bend it with your bare hands you won’t notice it bending visibly, but when you swing your club it does bend in an almost imperceptible amount. This can largely affect your game, especially if you are used to using another type of club with a different amount of flex. The main thing that changes your choice of flex is the speed of your swing.

When you choose which golf club to purchase here's something to think about - do you put all of your force and speed into a swing, or do you do it more delicately? The faster swings will probably be better off with a stiffer shaft. Club shops should be able to help you determine how much flex you need.