Project X PXi Iron Shaft from True Temper
Iron shafts are getting lighter. Lighter means faster, it means more maneuverable. Think of the difference between a Carbon Fiber Lamborghini and a Heavy Metal Chevy. The light weight Lamborghini accelerates quicker, there is less weight to get moving. It corners quicker because it has less centrifugal force acting on it. The Project X PXi is a lighter faster Project X. The 6.0 model lost 12 grams of weight and 2 pounds of butt stiffness. Does it work? Ask Jason Dufner and Ian Poulter, they are both using it. And we have Tiger and Rory using it in their utility/driving irons.
Loss of weight typically means loss of stiffness. As you can see, the average stiffness profile of the PXi is softer than the average stiffness of the Project X. Once again, we see stiffness numbers on a shaft that do not indicate an absolute reference. Do not take that comment as a criticism of True Temper. It is the same scheme used by every shaft company. That is one of the many reasons that club fitting is so critically important to game development.