Wilson Fi5 Forged irons. To reward the play of advanced shot makers, the weighting of the Wilson Fi5 progressively moves the centre of gravity from lower in the long irons to higher in the short irons. This is accomplished by concentrating weighting in the sole of the long irons, perimeter cavity back weighting in the mid irons, and pure muscleback weighting in the short irons. The Fi5 series is designed in the time-honored tradition of forged clubs, with thin top-lines and sole widths. 8620 mild carbon steel is used for maximum feedback at impact.