Mizuno Pro S-1 Irons: Everything you need to know

The Mizuno Pro S-1 irons are muscle-back irons built for the purist. Here’s everything you need to know about Mizuno’s latest Signature Series release.

I don’t know about you, but when I think Mizuno, I think about art and craftsmanship, the crème de la crème of golf irons. Many golfers believe the Japanese brand’s offerings are simply unmatched in terms of looks, feel, and quality.

For decades, Mizuno irons have been synonymous with forged excellence. Crafted in Hiroshima, Japan, using time-honored techniques and cutting-edge technology, Mizuno irons are renowned for their buttery-soft feel, elegant looks, and tour-validated performance.

From iconic blades like the MP-14 and MP-33 to the modern-day Mizuno Pro series, the brand has always championed precision and craftsmanship above all else.

Trusted by countless professionals, often even without an endorsement contract, Mizuno has earned a cult-like following among serious ball strikers. That legacy continues with the Mizuno Pro S-1, a muscle back designed for players who demand total control, maximum workability, and pure feedback.

What are the Mizuno Pro S-1 irons?

The Mizuno Pro S-1 irons are the latest addition to Mizuno’s revered Signature Series, designed for elite ball strikers who prioritise feel, control, and precision. These are true muscle backs crafted from a single billet of 1025E Pure Select Mild Carbon Steel using Mizuno’s advanced Grain Flow Forged HD process in Hiroshima, Japan.

Aimed at the game’s most exacting players, the S-1 offers a compact, clean aesthetic and pure forged feedback, but it’s more than just a throwback blade. Mizuno have implemented several subtle design innovations, many influenced directly by its tour staff, to elevate both the feel and performance of this iron.

Key technologies in the Mizuno Pro S-1 irons

Grain Flow Forged HD (High Density)

Mizuno’s famous forging process gets an update. Each S-1 iron is forged from a single billet of 1025E carbon steel in Hiroshima. The new high-density Grain Flow Forging enhances feedback and consistency while maintaining Mizuno’s iconic soft feel. The tighter grain structure is designed to improve both sound and responsiveness.

Channel Back Design

This isn’t your typical blade. Mizuno’s subtle Channel Back Design redistributes mass vertically for greater CG consistency and enhanced stability. It brings the center of gravity closer to the ideal strike point, which improves launch conditions while maintaining the solid, forged sensation that better players demand.

Harmonic Impact Technology (H.I.T.)

Feel isn’t just a sensation; it’s a science. Mizuno’s latest generation of H.I.T. takes that idea to the next level, using advanced software to fine-tune the sound and vibration of each strike.

By adjusting the clubhead’s internal geometry and shifting the key vibration frequencies, Mizuno has created a firmer, more responsive feel, without losing the classic forged softness. The result? Feedback that’s immediate, satisfying, and confidence-inspiring. It’s the kind of subtle refinement that elite players notice instantly.

Copper Underlay

Just like the popular Mizuno Pro 221 irons, the S-1s feature a thin layer of copper beneath the chrome plating. This layer subtly softens vibrations and enhances the feel at impact, creating what Mizuno describes as a “sensory connection” between player and club.

How does the sole design compare?

Mizuno has learned from tour feedback to reshape the sole of the S-1 for improved turf interaction, especially for shallower attack angles. Compared to the Mizuno Pro 241, the S-1 sole is flatter, has a sharper leading edge, and has one extra degree of bounce.

This makes it easier for the club to glide through turf without digging, encouraging more aggressive swings and confident ball striking.

What do the S-1 irons look like at address?

The Mizuno Pro S-1 features a compact, square-toe design with minimal offset and a thin topline. These visuals are influenced by tour players like Keith Mitchell and Ben Griffin, who prefer a more traditional, squared look. The head shapes flow more consistently through the set and match the Mizuno Pro S-3 profile for uniformity across the Signature Series.

What’s the finish like?

A full Nickel Chrome Soft White Satin finish gives the S-1 a clean, premium appearance. It’s the same glare-reducing finish found on the S-3 irons, offering enhanced focus at address in all lighting conditions.

Who are the Mizuno Pro S-1 irons for?

If you’re a confident ball-striker who values feedback, workability, and clean visuals over forgiveness or distance tech, the S-1 is likely your dream iron. It’s built for elite players who prefer shaping shots, controlling trajectory, and dialing in precision yardages.

Tour feedback was instrumental in the S-1’s development, making this one of the most refined muscle backs Mizuno has ever produced. It won’t be for everyone, but for the right player, it’s the ultimate tool.

If you think this is the club for you or you’re just interested in knowing what we thought about the club out on the course, then check out our full review of the Mizuno Pro S-1 irons.

Mizuno Pro S-1 specs and availability

• Available Set: 4-PW (Right and Left Handed)
• Shaft: KBS Tour 120 (Stiff flex standard)
• Grip: Golf Pride Tour Velvet
• Finish: Nickel Chrome Soft White Satin
• Release Date: Reviews go live from Monday, July 14, with presale starting August 28 and retail availability from September 11