When it comes time to reshaft your irons, reach for the True Temper Project X Rifle Shaft. A classic choice for all club makers and a proven winner on the PGA Tour. Patented Rifle design features a discrete constant taper for each Project X shaft. Longer taper rates result in more energy transfer to the ball resulting in a higher trajectory, that flattens out quicker, for increased distance and carry. Temper Temper Project X shafts use a more precise, Frequency Matched (FM) system, for measuring flex. The number on each shaft represents a frequency in cycles per minute to precisely define the shaft's flex. When built correctly, to True Temper's specifications: 5.0 flex equates to a regular flex, 5.5 flex equates to a regular+ flex and 6.0 flex equates to a stiff flex.