This process assures that all shafts within a matched set have identical flexibility. In sets that are not frequency matched, golfers may find slight variations in flex from one club to the next, even in shafts that are all labeled the same (stiff, regular, etc).
A shaft’s frequency is the amount of oscillation that occurs when the head end is pulled and released. Faster oscillation (higher frequency) equates to greater stiffness. Shaft frequency also increases as length decreases. In a frequency-matched set, the increment of frequency increase is exactly the same from one to the next.
Clubmakers including Thomas Golf (www.thomasgolf.com) offer frequency-matched shafts at no extra charge.