Soft carbon steel irons bend easily for fitting
The instructor notes the short irons are a softer carbon steel (8620), and that softness is what gives the ability to bend the clubs easily during the fitting. He contrasts this with the previously tested Cobra irons, which were cast and really firm. The practical point: a soft carbon steel iron body can be bent easily, while a firm cast head resists it.
Channel: Club Champion
Watch official source at 3:40Why this context matters
Comparing to previously tested cast one-length irons.