After the success of infusing 1025 carbon steel with the metal boron in the JPX850 Forged irons, it was only a matter of time before Mizuno applied the same idea to an MP iron.
The advantage of using boron steel in the MP-25 irons is that it is stronger than normal 1025 carbon steel, yet still soft enough to forge and bend if required.
The boron steel still uses the grain flow forging process that Mizuno has been using for the past 30 years to ensure a consistent feel through each head in the set.
This boron steel enables Mizuno to make the face of the MP-25 thinner and place a small Micro-Slot pocket cavity in the 3- to 6-irons that allow it to flex a little to increase ball speeds.
In the shorter irons, the Micro-Slot is not required as the higher loft on the face creates more of a glancing blow….READ FULL ARTICLE HERE