Sept. 3, 2026, 9:30 a.m. ET
The Mizuno Pro S-4 irons are designed for skilled golfers seeking more forgiveness than traditional blades.Each club is forged from carbon steel with a copper underlay to enhance feel and feedback.These irons feature a wider sole and lower center of gravity to help launch the ball higher.Design features like offset and topline thickness progressively change throughout the set for optimized performance.
Gear: Mizuno Pro S-4 irons
Price: $215 per club with a True Temper Dynamic Gold Mid 115 Stiff shaft and Golf Pride Z-Cord grip
Specs: Grain Flow Forged HD 1025E Pure Select Mild Carbon Steel with a copper underlay. Available in 3-iron through pitching wedge for right-handed golfers and 4-iron through pitching wedge for left-handed golfers. Lofts range from 21 to 46 degrees.
Available: Sept. 17
Who it’s for: Accomplished golfers who want the compact shape, feedback and control of a Mizuno Pro iron, but need more launch and forgiveness than a traditional muscleback or compact players cavity provides.
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What you should know: The S-4 is Mizuno’s most forgiving Signature Series iron, with a lower center of gravity, wider sole and more offset than its stablemates. It is designed to launch shots higher and produce more consistent results on off-center strikes while preserving the look and forged feel better players expect.
The Deep Dive: Forgiveness in better-player irons is a bit like hot sauce. Some low-handicappers want it, but they do not necessarily want everyone at the table to see them pouring it on. The Mizuno Pro S-4 was designed for those players.
The newest member of Mizuno’s Signature Series joins the S-1 muscleback and S-3 players cavity-back, expanding a family created around the idea that accomplished golfers do not all want the same thing from an iron. The S-1 prioritizes workability and direct feedback, while the S-3 (which ironically was the first club in the family released) adds stability. The S-4 moves another step toward playability, although its compact profile keeps it firmly in the better-players iron category.
Each S-4 head is forged in Hiroshima, Japan, from a single billet of 1025E Pure Select Mild Carbon Steel using Mizuno’s Grain Flow Forged HD process. A copper underlay is intended to soften and refine impact vibrations, while Harmonic Impact Technology tunes the sound and feedback.
The result is an iron aimed at golfers who still care how a club looks behind the ball and feels at impact, but have reached the sensible conclusion that a little assistance is not a character flaw.
Mizuno reshaped the muscle in the back of the S-4 with softer, curved geometry that shifts more mass lower in the head. The company also gave the iron a wider sole, a deeper center of gravity, a lower sweet spot, and slightly more offset. Working together, those changes should make the long irons easier to launch and help shots struck outside the center of the face fly more consistently.
The shaping changes progressively through the set. The long irons have more offset and a slightly thicker topline to inspire confidence and increase forgiveness. As the clubs get shorter through the mid-irons and scoring clubs, the offset and topline thickness are reduced, creating a more compact appearance for golfers who want to flight the ball and control distance.
The Triple-Cut Sole has beveled leading and trailing edges. That geometry is designed to help the head enter and leave the turf more efficiently, preserving speed through impact from different lies instead of digging like a garden shovel when contact gets steep.
So yes, there a little hot sauce in the Mizuno Pro M-4 iron’s recipe. Mizuno just kept the bottle off the table.
David Dusek is a senior writer at Golfweek covering golf equipment and analytics.