Classically Modern – The New Mizuno Pro M-13 And M-15 Irons

When it comes to compact, better-player irons, Mizuno’s pedigree is well established. As such, I don’t expect that the new Mizuno Pro M13 and M15 irons will stray too far from that identity.

Typically, with a product launch, it’s the first time that we’re able to publicly share technical details, key techologies and pricing information. However, a good bit of these particulars are already pasted on the internet. That’s thanks primarily to a staggered global release, whereby Mizuno first launched the M13/M15 irons nearly five months ago in Japan. Now, the U.S./Europe and the rest of the world get the goods. Fingers crossed, this should be the last time we’re in such a situation. But don’t allow that slight annoyance to sully your spirits: it’s game time!

Mizuno Pro Family Tree

The Mizuno Pro family of irons is separated into two lines: the “S” that features timeless design elements and a four-year product life cycle, and the “M” with timely, modern platforms and a more industry-standard two-year life cycle.

If you’re familiar with Mizuno’s iron lineage, the “S” models (S3 and S1) are emblematic of the traditional, single-piece forged irons that dominated damn near every equipment count in the 1990s. They are the single-piece, grain-flow forged muscle-backs and player’s cavity-back irons that deliver the signature Mizuno feel, which has served as a de-facto industry benchmark since Nick Faldo was winning majors.

The “M” line leverages more complex constructions, using multiple materials and design elements that generate a combination of ball speed, trajectory, and control that should compete favorably against anything on the market.

Mizuno Pro M-13 – Construction and Tech

Using Mizuno’s parlance, the M13 is a “Player’s Speed Cavity” which should tell you that the primary design goal is some combination of a traditional player’s cavity-back but with a bit more horsepower.

Speed often comes at the cost of feel, something Mizuno isn’t willing to concede. Mizuno notes that many competitors produce “forged” irons but rely on a welded-face construction. Effectively, the face is a separate piece that is affixed (generally welded) to the body as opposed to a single piece of forged steel containing the face and neck. This matters because multiple pieces don’t allow for a continuous grain flow (the microscopic crystalline structure of forged steel) from hosel to toe. Without this uninterrupted neck-to-toe span, it’s damn near impossible to generate that soft, solid feel that players expect from a forged iron. And it’s why the tagline “Nothing feels like a Mizuno” persists. Plus, “be wary if your forged iron doesn’t have the face and neck forged as a single piece” is a mouthful. In addition, the M-13 irons feature a layer of copper under the chrome plating, which Mizuno brought back for the MP20 line of irons in 2019.

Overall, the complex construction of the M-13 acts as a combo set within a single model. Really, it’s three distinct constructions in a single set of irons. The long irons (4 and 5) use an HD 4120 forged face and neck with a 431 stainless-steel back, similar to the JPX 925 forged construction. The “Contoured Ellipse” face – a first for Mizuno in a high-COR iron – increases both the central COR and overall core area. While the concept of variable-face thickness isn’t new – and Mizuno isn’t suggesting that it is – continual improvements in face topography yield incremental performance benefits. The face is forged to a minimum thickness of 1.37 millimeters, which is 35 percent thinner than the MP 243 long irons, making it Mizuno’s highest COR forged iron.

The mid-irons (6-8) are, again, one-piece grain-flow forged, this time from 4115 Chromoly and designed with Micro-slot (open cavity) technology. Starting at the topline and moving down to the sole, the face thickness decreases from 3.0 mm to 2.0 mm – the net result is a 0.3 mm thinner face behind impact (compared to the MP 243).

Finally, the 9i-GW offer the simplest construction – a pure, one-piece forging using the same HD 1025 Elite carbon steel as the S1/S3 kinfolk.

M13 – A word about the sole

The M13 irons utilize a triple-cut sole (although I’d argue it’s more like three surfaces and two cuts but alas). The leading-edge bevel produces a high-bounce surface, which keeps the club from digging when entering the turf, and then the trailing-edge relief reduces drag for a clean exit.

Bottom line? Many golfers (myself included) noted that the MP 243 was faster than they expected. Some tour players don’t need or want the additional speed, but the rest of us won’t turn down a couple of extra yards. Compared to its predecessor, the M13 is slightly more compact heel-to-toe, yet more forgiving with a little more ball speed. This translates to greater max peak height and several additional yards of carry. And I have it on good authority that the signature MP feel remains intact, although I look forward to confirming that myself.

M15 – Tour Speed and Launch

The M15 is an updated hollow-body design, again with three individual constructions throughout the set. The 4- to 7-irons are grain-flow forged from 4135+ Chromoly (face and neck) with a 431 stainless steel back plate. Also, a heavy nickel-tungsten weight “floats” low/deep in the clubhead to promote higher launch. One benefit of a hollow body is that engineers can manipulate mass properties inside the open structure to impact ball flight. In general, the Mizuno Pro M-15 target buyer could benefit from a higher overall ball flight, particularly in the long irons.

Moving to the middle of the set, the 8-iron is the same as the 4i-7i, but without the nickel-tungsten weight. Finally, the 9i-GW feature a semi-hollow cavity inside a grain-flow forged HD 1025E body and 17-4 stainless steel back piece.

The takeaway is that Mizuno separates the M13 and M15 primarily by launch profile, with the M-15 offering a higher overall flight than the M-13. The flighted nature of the M15 should produce higher launching long irons and relatively lower, more penetrating, scoring irons. Comparatively, the M13 should be slightly hotter/faster throughout the set with a more penetrating trajectory. I don’t know that it’s reasonable to put a firm handicap designation on either model, but both sit comfortably in the “Players” category.

Mizuno Pro Fli-Hi

The new Mizuno Pro Fli-Hi utility iron adopts a multi-piece construction (4335+ nickel-chromoly body and a firmer heat-treated 4335+ L-face). Also, a thinner contour ellipse face helps generate a 38-percent increase in core area, which is a notable improvement. For the record, core area is the portion of the face with a COR value of 0.833 or higher. If you don’t care about the numbers, all that matters is that you should get higher, and more consistent, ball speeds with the ’26 version as compared to the ’24 model.

Of equal importance, a 26-gram weight bar (three grams more than the ’24 MP Fli-Hi) sits low/forward in the clubhead for easier launch, which is the primary performance attribute of this club. The discretionary weight pushes the CG slightly forward for a net benefit of nearly two mph ball speed, four yards of carry, and a slightly steeper (two degrees) descent angle, according to Mizuno’s testing. It’s a niche category, though with the increased popularity of higher-lofted fairway woods, the MP Fli-Hi provides a nice alternative for golfers looking to replace traditional long-irons or as a 15th club to swap out based on course set up.

My $0.05

Innovation doesn’t look the same for every manufacturer or every equipment category. But what remains true is that giving golfers more of what they want and less of what they don’t is a solid recipe. In Mizuno’s case- and specific to the MP iron franchise – that means finding ways to shrink the footprint, thin out the topline, improve turf interaction, all while retaining the signature Mizuno Pro feel and eeking out a bit more ball speed.