Mizuno Pro S1 Irons Review: Precision with a Price

There’s something deeply satisfying about hitting a pure iron shot. The kind that launches on a rope, climbs with intent, and comes down like a dart.

I got that feeling often during the 6 years I gamed the Mizuno JPX-900s. Those irons were lethal when I was on my game. Not the most forgiving clubs I’ve ever used, but when I was swinging confidently, they felt like an extension of my body.

Fast forward to today, and I’ve been testing something entirely different: the brand new Mizuno Pro S1 irons. These are not game improvement clubs. They’re not even “player’s distance” irons. These are pure, forged blades made for golfers with a swing much more consistent than mine. But that didn’t stop me from giving them a go. And I’ve got thoughts.

First Impressions of the Mizuno S1 Pro Irons

Let’s get this out of the way: these clubs are stunning. The Mizuno Pro S1s look like they belong in a museum display case, not a Sunday morning muni round. The Soft White Satin finish is subtle and classy, and the blade profile—especially the square toe that tour guys like Keith Mitchell and Ben Griffin prefer—gives off serious “no nonsense” vibes.

Coming from the PXG 0311 XP irons I’ve been gaming recently, the S1s look like absolute butter knives. The 0311s are good clubs for the mid-handicapper, but sitting the S1 down behind the ball makes you feel like you’ve stepped into a completely different world. The S1 just begs to be struck well. Whether or not you can actually do that consistently is another question.

Mizuno specced my review set with KBS Tour 120 stiff shafts and a -2 adjustment, and even just wagging them at address gave me that “Tour” feeling.

These irons feature Mizuno’s Grain Flow Forged HD process using 1025E Pure Select Mild Carbon Steel. And yes, that’s a mouthful, but it’s also what gives Mizuno irons their famously buttery feel. That feel is further dialed in by a copper underlay and Harmonic Impact Technology (H.I.T.), which fine-tunes vibration for ultimate sensory feedback.

Spoiler alert: you can tell.

Performance and Feel of the Irons

Standing next to my buddy Jeff, who plays the previous generation Mizuno Pros, we lined them up and—unsurprisingly, the S1s are similarly tiny.

Not intimidating, but… let’s say “respect-demanding.” You look at the face and think: This is a test of skill, not forgiveness.

But when you catch one flush? Holy hell.

The first time I pured a 5-iron and watched it fly 190 yards straight onto the par 3 5th at Ghost Creek, I said out loud, “Oh, I can totally play these.” That confidence didn’t last forever, but that’s part of the magic of the S1. Good shots feel fantastic. Crisp. Soft. Pure. Like the club disappears, and all you remember is the strike.

The Channel Back Design redistributes mass to keep the vertical CG consistent, which helps with launch predictability, especially for better players. And the sole—refined through Tour input with a flatter camber, sharper leading edge, and more bounce—glides through the turf with precision, particularly if you have a shallow angle of attack.

But if you don’t catch it clean? You’ll know. You’ll feel it. You’ll see it. These are not clubs that cover up your mistakes. They expose them. Brutally, but honestly.

Who are these for?

Let’s be clear: these are for elite ball strikers. Low single-digit handicaps and better. If you consistently find the center of the clubface and want maximum feedback and control, the S1s are exactly what you’re looking for.

But what I’ve always loved about Mizuno is how their attention to feel and craftsmanship isn’t limited to just their tour blades. That same DNA runs through more forgiving lines like the JPX series—clubs like the 900s or the newer JPX 923 Hot Metals that I’d recommend to almost any mid-handicapper.

Final Thoughts on the Mizuno Pro S1 Irons

The Mizuno Pro S1 irons are unapologetically demanding. They reward pure contact like few other irons on the market—but they don’t hand out second chances. If you’re a player who can live up to that standard, these are some of the most underrated, best-feeling irons you can get your hands on.

That level of craftsmanship doesn’t come cheap. At $215 per club, a full set of S1s will run you around $1,500 at retail, which puts them right in line with other premium tour-level blades. But unlike some of the flashier brands that push marketing louder than performance, with Mizuno you’re paying for heritage, precision, and feel that has been player-tested and tour-validated for decades.

For the rest of us? Don’t be fooled by their beauty. There are other options out there that offer a similar Mizuno feel, with more forgiveness and distance built in. The S1s are a scalpel, not a Swiss Army knife. And while I’m glad I got to swing them, I’m also a little relieved to go back to something with a little more margin for error.

That said… that one pured 5-iron? I’ll be thinking about it for a while.