Mizuno Pro S-1 irons: A modern muscleback forged for precision and solid feel

USA Today

a day ago

The Mizuno Pro S-1 irons offer a pure muscleback design with refined feel, stability, and tour-inspired shaping.
Gear: Mizuno Pro S-1 irons
Price: $1,400 (7-piece set) with KBS Tour 120 stiff shafts and Golf Pride Tour Velvet grips
Specs: Grain Flow Forged HD 1025E mild carbon steel, Channel Back design, copper underlay, Harmonic Impact Technology
Available: Pre-sale begins August 28; retail release September 11
Who it's for: Elite golfers who prioritize feel, precision, and control above all else and prefer a compact, pure muscleback iron with modern sole geometry.
What you should know: The Mizuno Pro S-1 brings classic forged feel and shaping to a modern muscleback with refined sole geometry, enhanced vertical stability, and a satisfyingly solid feel preferred by discerning ballstrikers. It blends seamlessly with the S-3's Signature Series while having sharper shaping and tour-validated sole refinements.
The Deep Dive: The Mizuno Pro S-1 irons continue a tradition of precision-forged, tour-inspired blades with subtle yet meaningful updates that make them more playable and more refined — without losing the DNA that's earned Mizuno its reputation among ball-strikers.
Where the Mizuno Pro S-3 irons that were released in 2024 provided a tiny bit of forgiveness through a subtle cavity-back and multi-material construction, the S-1 is a pure muscleback for elite players who want control, workability, and a direct connection to the golf ball. But this is more than a nostalgic blade—it's a modern, optimized evolution.
The S-1 is forged from a single billet of 1025E Pure Select mild carbon steel using Mizuno's Grain Flow Forged HD process in Hiroshima, Japan, creating a tight grain structure for that buttery-soft feel Mizuno fans expect. A thin copper underlay sits beneath the chrome plating to subtly soften vibrations, enhancing feedback without sacrificing a crisp, solid sensation through impact.
What distinguishes the S-1 is the Channel Back design, which strategically repositions mass behind the face to promote greater vertical stability and a more consistent center of gravity. This tweak yields more consistent launch and control, especially on slightly mishit shots, without compromising the look of a traditional muscleback.
Harmonic Impact Technology (H.I.T.) returns with fine-tuned vibration frequencies that produce a slightly firmer, yet satisfyingly-solid feel at impact. It's designed for players who want auditory and tactile feedback that breeds confidence with each strike.
Visually, the S-1 stands out with a square toe shape, a look that has gained popularity on tour and resonates with players like staffers Keith Mitchell and Ben Griffin. Compared to the more rounded S-3, the S-1 has a more compact, squared-off profile, especially in the scoring clubs, to create a sharper, more defined look at address.
The sole geometry — refined with input from tour players — features a flatter camber, sharpened leading edge, and an extra degree of bounce compared to the S-3. This combination smooths out turf interaction, particularly for players with a shallower angle of attack, and helps avoid digging while maintaining the ability to play aggressively off tight lies.
Available in 4-PW for both right- and left-handed players, the S-1 comes standard with KBS Tour 120 stiff shafts and Golf Pride Tour Velvet grips. The loft progression starts at 24 degrees in the 4-iron and ends at 46 degrees in the pitching wedge, keeping pace with modern gapping expectations while maintaining classic feel and control.
In the end, the S-1 isn't about chasing distance—it's about delivering precision, consistent launch, and the kind of refined feedback that players at the top of their game demand. Where the S-3 catered to elite ball-strikers who wanted a bit of help, the S-1 is for those who want nothing to come between them and the golf ball.