Iron golf club set

A golf club iron set comprising:

• a plurality of golf club irons of different counts and of correspondingly different lengths, each golf club iron having a steel shaft, a grip end, and a head sole end, the steel shaft of a shorter of the plurality of golf club irons being heavier than that of a longer of the plurality of golf club irons;
• the steel shaft of each golf club iron having:
• a step formation region spaced by a first axial distance from the grip end thereof, the first axial distance being equal for all of the plurality of golf club irons, an outer diameter in the step formation region differing in a plurality of steps;
• and
• a specific area of steps within the step formation region and spaced by a second axial distance from the head sole end thereof, the second axial distance being equal for all of the plurality of golf club irons and placing the specific area nearer to the grip end than to the head sole end, an interval between steps in the specific area being smaller than an interval between steps in the step formation region outside of the specific area.