Aerotech Steelfiber Black Label Private Reserve I90 Iron Shaft .355 SpinnerATSFI90BLKRSVW Specifications SteelFiber Private Reserve With more professional tour wins than any other graphite iron shaft in history, SteelFiber iron shafts are the preferred option by the world's best. SteelFiber Private Reserve shafts take that excellence to the next level by providing Aerotech's unique SteelFiber technology in a range of shafts that feature ultra tight tolerances for the player seeking the best. SHAFT FLEX LENGTH WEIGHT (g)