Mizuno Pro S-4 Irons Review

I’ll be honest, I find Mizuno’s iron release schedule a bit confusing, and I think the more discerning golfer in the UK market might feel exactly the same.

Their lineups just don’t feel as clearly thought out as some of the other leading manufacturers, and I think that hampers things because it can actually be hard work out which irons are best for different golfers.

We reviewed Mizuno’s M-13 and M-15 irons at the start of this year and I was really impressed with both of them. So going into testing the Pro S-4, I wanted to find out where they fit into Mizuno’s lineup, and whether they can live up to the standards set by the M range at the start of the year.

Who Are They Aimed At?

Mizuno’s current iron lineup genuinely blurs into one a bit, so here’s the tale of the tape before we get into the S-4 itself:

• Mizuno Pro S-1 – a proper tour blade, a traditionalist’s iron for elite ball strikers.
• Mizuno Pro S-3 – for scratch golfers, still great ball strikers, and some tour players will likely use these as a combo set alongside the S1.
• Mizuno Pro S-4 – the iron on test here, and officially the most forgiving in the Signature series, for scratch golfers moving into single figures.
• Mizuno M-13 – a players distance iron for single figures moving into the early teens.
• Mizuno M-15 – a sightly stronger, more forgiving players distance irons for handicaps into the teens
• Mizuno JPX range – Mizuno’s most forgiving game-improvement irons, with more emphasis on ball speed, largely aimed at mid-handicappers and above.

So the S-4 is really for the scratch-to-single-figure golfer who wants that classic Mizuno look and feel, without going all the way to a full blade.

The Tech

The standout feature here is a redesigned cavity back, which repositions mass through increased offset, a wider sole, a lower sweet spot height and a deeper centre of gravity.

Mizuno says that this helps to promote a higher launch, increased stability, and improved forgiveness on off-centre strikes, without giving up the precision that you’d expect from a Mizuno players iron.

It’s progressive throughout the set, so the longer irons have more technology around forgiveness, while the scoring clubs transition towards a more compact profile.

That sits alongside a Triple Cut Sole, with bevelled leading and trailing edges said to improve turf interaction for a smoother entry and exit through impact. This results in a unique-looking sole shape compared to most other irons out there.

As you’d expect from Mizuno, the iron is forged from a single piece of 1025E Pure Select Mild Carbon Steel using their patented Grain Flow Forged HD process in Hiroshima, Japan, with a copper underlay to enhance the soft, responsive feel.

Mizuno’s Harmonic Impact Technology (HIT) precisely tunes the head’s vibration characteristics, aiming for a solid, refined feel at impact.

Looks

This is genuinely the most Mizuno-looking Mizuno iron I’ve ever tested. The slight curvature they’ve added to the cavity softens what is otherwise quite an angular, almost boxy head shape at address. The shaping around the top of the toe is quite severe rather than nicely rounded like some other irons, but I don’t dislike that.

It’s a classic Mizuno design. I like the Mizuno Pro branding, the simple Runbird logo, and the brushed chrome finish, which they’ve used across most of the range for a while now.

The blade length is on the longer side, which makes the top line look thinner and the head somehow less forgiving, even when it isn’t. This is more of a personal preference really, whether you’re into thinner, longer lines, or something shorter and more compact.

Feel

I’d echo what Ben found when he tested the Pro S-1 last year, these don’t feel amazing, buttery, or especially soft.

What they do feel is really responsive. You know exactly where the ball’s come off the face, even if the sensation itself is quite muted, almost numb. You can strike one off the toe and it doesn’t feel awful, but also if you hit one out of the screws and it doesn’t feel amazing either.

There’s a real consistency to that, but if you’re an absolute purist who thinks nothing feels like a Mizuno, I didn’t massively find that here.

Sound-wise, despite the fact that it’s built to be more forgiving you still don’t get a hollow sound, and there’s a decent punch to it.

Mizuno’s Harmonic Impact Technology is designed to tune the vibrations and create a solid, refined feel and sound and I have to say it does that. There’s next to no vibration to it at all, which adds to that numb feeling again. Whether that counts as “exceptional,” like Mizuno’s own materials claim, is personal preference. For my taste, I wouldn’t go that far.

Performance

I tested the new Pro S-4 irons on the GC Quad and found that the data backed up pretty much exactly what I saw on the course.

The 7 iron was producing an average ball speed of 118.5mph, a launch angle of 19.9°, spin rate of 6,670rpm, and an average carry of 163.5 yards (172.8 yards total), with a peak height of 106.6ft. My carry numbers dropped as low as 158 yards on mis-hits and up to nearly 172 yards on my best strikes.

I was genuinely surprised by the lack of distance here, especially given this is meant to be the most forgiving iron in the Pro series. I’m not saying they’re short, but that easy, effortless distance you get from some irons just isn’t really there.

Where they did impress was the 5-iron. It launched high, and I didn’t feel like I was losing out on distance off the tee even hitting a couple into the wind. You’re not going to get any low-spin bullets out of these, but they still did the job nicely.

I enjoyed hitting the long irons in general – I like the longer blade length, I like the thin top line, and I like hitting long irons into greens and off tees, which these let me do well.

There’s definitely workability in there too. It felt a little spinny at times, which may have cost a touch of control, though that could just be a byproduct of the higher launch. Turf interaction was good throughout. with the club exiting the turf cleanly and producing nice compact divots. Perhaps that’s the Triple Cut Sole working it’s magic!

Verdict

These are really nice irons, but those more traditional lofts mean they’re always going to lose out a little on distance against the irons they’re really up against, which leave the Pro S-4 a bit stuck in no man’s land. That’s not to say they’re a bad iron, or that I didn’t enjoy hitting shots with them. It’s more that, having tested them, I don’t feel any clearer on exactly who should be playing these.

There are other irons out there that’ll give you a bit more distance, a bit more control, and a bit more forgiveness, while looking and feeling nearly as good – for potentially less money.

At £215 per iron, you’re looking at roughly £1,500 for a full set, which is pretty expensive, although the overall finish and premium look is impressive.

If you’re currently gaming something like a Titleist T250 or a Mizuno M-13, you’d gain a bit more feel moving to these, but you’d lose out on distance and forgiveness.

A lot of this comes down to where the market’s at with iron lofts right now. With lofts creeping stronger across the industry, seeing 163 yards out of a 7-iron feels disappointing purely because we’ve become used to seeing more. That’s not really a criticism of the S-4 specifically, more a reflection of where iron design is at the moment.

Would I Use Them?

Yes I would. I would have to put up with losing a bit of distance, but I feel like there’s just about enough forgiveness in there, combined with great looks and feel, to make these a good option.

Frequently Asked Questions

How much does the Mizuno Pro S-4 cost?

The Mizuno Pro S-4 has an RRP of £215 per iron, working out at around £1,500 for a typical 3/4-PW set.

Who are the Mizuno Pro S-4 irons aimed at?

They’re aimed at scratch golfers moving into single figures — sitting just below the Pro S-3 in Mizuno’s Signature series, with more forgiveness than a full blade but still very much a players iron.

What’s the difference between the Mizuno Pro S-4 and the Pro S-3?

The S-4 uses a redesigned cavity back with more offset, a wider sole, a lower sweet spot height, and a deeper centre of gravity, to promote a higher launch and greater forgiveness than the more compact, tour-focused S-3.

How does the Mizuno Pro S-4 compare to the Mizuno M-13 and M-15?

The M-13 and M-15 sit in Mizuno’s newer, more distance-focused line, and in our testing offered noticeably more distance than the S-4. The S-4 leans more towards feel, workability, and a classic Mizuno look, at the cost of some outright yardage.