When Mizuno sets out to update their legendary muscleback irons, they make changes in small, incremental steps, in order to preserve the time-tested design. The new Pro 221 Iron, which replaces the outgoing MP-20, has evolved to be more playable through refinements in shape and weight placement. Mizuno bevelled the irons to deliver the appearance of a shorter face profile and narrower topline, without eliminating the always-important upper blade mass. The Pro 221 is Grain Flow Forged in Japan from 1025E Pure Select mild carbon steel, then plated in soft copper and Nickel Chrome, the original layering from Mizuno's iconic TN87 blade. Mizuno returned to the soft copper underlay in 2019 after tour professionals unanimously preffered the feel during testing.