When it comes to player feedback, there are few companies more respected than the ones based out of Japan. The Mizuno Pro S-4 irons are built to offer exactly that and more beyond.
In days gone by, had you asked any golfer which iron brand was considered the ultimate sign of a true player, there was only one answer: Mizuno.
Nowadays, there’s certainly far more competition for that position, but with the release of the new Mizuno Pro S-4 irons, Mizuno are looking to cement their spot as the iron connoisseur’s choice.
So far, the Mizuno Pro Signature series, made up of models built to a classic style with longer product lifecycles, has been limited to tour-caliber designs in the Pro S-1 and S-3 irons seen in the hands of elite ball strikers like Ben Griffin and Keith Mitchell.
In the Mizuno Pro S-4, Mizuno are bringing together everything that appeals to advanced players in those other models while enhancing off-center assistance to appeal to a wider range of players.
Quick Verdict
The Mizuno Pro S-4 irons are one of the most impressive players’ irons that I’ve tested in years. The push from Srixon for top spot in the Japanese brand battle seems to have only driven Mizuno further on, with the new model being one of the most versatile offerings in the category.
The latest Signature series blends the best of classic Mizuno looks and feel with modern sole design and CG placement to create an iron that could well be an iron we continue to talk about for years to come.
Signature feel, surprising forgiveness
Pros & Cons Ratings Specs Features
Pros New curved muscle shaping provides impressive forgiveness for the head sizeFeel is still one of the most impressive on the marketTriple Cut Sole continues to be a highlight for smooth ground contact Cons I feel the S-4 irons are going to mainly be used as long iron replacements
Looks/Feel
Technology
Performance
Overall
RRP $1,505 / £1,505 Availability 3-PW Stcok Shaft Dynamic Gold Mid 115g Stock Grip Golf Pride Z-Cord 7-iron Loft 34º Category Player’s Cavity Construction Grain Flow Forged HD 1025E Mild Carbon Steel Mizuno’s classic 1025E Grain Flow Forged HD steel provides best-in-class feelTriple Cut Sole maximizes turf interaction fluidity for consistency across ground typesCopper Underlay and Harmonic Impact Technology fine tune feedback across the faceProgressive head geometry for optimized ball flight conditionsRedesigned curved muscle provides greater stability while maintained the Mizuno Pro Signature series profile
Looks/Feel: 5/5
Thinking back, I don’t think I’ve ever given a Mizuno forging less than a perfect score for this category and it’s with very good reason.
Now, I will accept that some of that comes from a deep love of the styling produced by the manufacturer, but I honestly defy anyone to look down at the Mizuno Pro S-4 irons and not fall in love with the shaping, the attention to detail, and the craftsmanship on display.
There are clear through-lines to some of the best irons Mizuno have ever produced. The S-4 is a showcase, in my mind, of style influences from early 2010 models like the MP-52 and MP-62, as well as the more recent MP-18 SC and MMC, coupled with the contemporary design and fashion of modern Mizuno.
This also extends to the brushed finish in the rest of the Signature series. With most other models I see in this look, like Wilson’s Staff Model Blades and CB irons, I struggle to become comfortable. They usually appear to take on a foggy, almost cartoonish or comic book-like appearance, but the Pro S-4 manages to balance the satin in a way that still looks true to the quality of steel underneath while holding off from the complete mirror finishes the older heads are known for.
I want to expand a little more on feedback as part of our ‘performance’ section, but the tiny reservation I had from the bigger brother M-13 irons with the altered construction is firmly gone here.
The Pro S-4 irons are everything that I expect from a premium set for feel and embody exactly what you want from a tour-level product.
Technology: 5/5
That distinctive quality of feedback (‘nothing feels like a Mizuno’, as their marketing likes to say) is no accident either.
Yes, there’s the usual 1025E mild carbon steel, built using the patented Grain Flow Forged HD process that Mizuno have used for years, as well as the layer of copper that’s added over the top of the raw steel before the aforementioned final brushed finish is applied.
That underlay allows for a firmer steel to produce slightly more ball speed without a reduction in ‘softness.’
In addition, Mizuno have utilized their Harmonic Impact Technology (HIT) to take their emphasis on feel even further. HIT analyzes the frequencies produced by an iron when struck and allows the engineers to alter geometry or material placement to hit that golden zone for player-preferred sound.
Speaking of geometry, the Mizuno Pro S-4 head features a progressive head shape that addresses offset changes, Center of Gravity (CG) locations, and sole width throughout the set for consistent performance.
This also includes the redesigned curved muscle, which alters that CG for easier launch and higher trajectory flights, and the Triple Cut Sole made famous by Brooks Koepka’s before he signed (and then unsigned) with Srixon.
Triple Cut is a distinct camber on the base of the club to promote faster, smoother entry and exit from a variety of lies and turf conditions, allowing the golfer to transfer their delivery to many different course setups without difficulty.
It’s a combination of technologies that help to bring out the best in a ball-striker’s performance and offer that extra little bit of help when required.
Performance: 5/5
On the course, the Mizuno Pro S-4 irons are absolutely outstanding. The technology and looks work in tandem to provide the golfer with real confidence that the ball is going to move how and where you want it to, even without a perfect impact.
The additional lower mass in the refined muscle, as well as the Triple Cut, make these irons a dream to strike and flight. The width in the sole never feels unwieldy due to the improved camber – not that the width is particularly dramatic anyway – and that’s been in both the firm summer and slightly softer wet conditions I’ve tested in.
I’m also a big fan of the offset included. It’s not heavy-handed, but you’ll notice it if you compare it to another player’s CB or muscleback iron.
It’s considered old-fashioned now, but it’s a touch that makes delivery feel more passive through my hands, with less reliance on an aggressive release or body turn to square the face.
My only somewhat negative thought on these irons is that I don’t think enough golfers will see these as a full set options, instead pairing them with S-1/S-3 as long iron replacements, or having these in the short irons and M-13 in the longer end of the bag.
That’s a shame, because the design and engineering that’s gone into these clubs makes them extremely playable from the 3-iron through to the pitching wedge.
Overall: 5/5
If you’re looking for the best blend of feedback, turf interaction, distance control, and that extra inclusion of forgiveness while retaining a player’s iron shape and size, I think the Mizuno Pro S-4 irons have to be on your radar.
It’s been one of my favorite irons to test since I began reviewing golf clubs, and I would thoroughly recommend the S-4 for many different levels of golfer, from professional to amateur.
This is an iron that’s going to be in the conversation for a long time, and I can’t wait to see how players compare it to the best models in the category.
For me, Mizuno are putting forward the strongest case they can for why they should still be the first thought in the premium iron space, and 2027 might already be one of the best years we’ve ever seen for a players’ iron battle.
Similar Irons to consider…
Modern demands in a precise package
Pros & Cons Ratings Specs Features
Pros Outstanding performance within the Player’s CB categoryBeautiful looks with classic Mizuno styleConsistent apex throughout the set Cons Long-time Mizuno users may notice a feel change
Looks and Design
Technology
Performance
Overall
RRP $215/£240 per iron Availability 4 – PW, GW Stock Shaft Modus Tour 120 (Steel) Stock Grip Golf Pride MCC Black/Grey 7-iron Loft 32° Category Player’s Cavity Construction Grain Flow Forged HD 4120 Nickel Chromoly (4-8i), Grain Flow Forged HD 1025E Stainless Steel (9-GW) Modern series design brings together performance and styleThree distinct forging technologies create perfect flight consistencyTriple Cut Sole for improved turf interaction in any conditionHigher speeds and launch from long iron-specific constructionImproved sound through Copper Underlay and Harmonic Impact TechnologyFinished in a Nickel Chrome Satin overcoat
Complete control with surprising forgiveness
Price: $1,399.99 / £1,169.00
Pros & Cons Ratings Specs Features
Pros More forgiving than expectedSits really invitingly at addressOptimal spin and performanceLooks incredible Cons Weak lofts might need strengthening for some golfers
Looks and Design
Technology
Performance
Overall
RRP $199.99 / £167.00 per iron Availability 3 – GW Stock shaft True Temper Dynamic Gold Mid 115 – R (114g), S (115g) Stock grip Golf Pride Z Grip 7-iron loft 34° Category Players’ cavity Construction Forged 8620 Carbon Steel Fluid Feel HoselPrecision Milled FaceForged 8620 Carbon SteelBrushed satin finishModern head shape