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Mizuno ST-G driver (2023): What you need to know

October 05, 2023

WHAT YOU NEED TO KNOW: The new Mizuno ST-G driver features the compact pear shape and deep face that better players naturally gravitate to, but it expands the range of appeal through enhanced adjustability, the increased flexibility in the face fueled by a new beta rich, lighter and stronger titanium alloy and the low-spin effects of a weighted through-slot in the sole.

PRICE: $600, 9.5 and 10.5 (adjustable). At retail Oct. 5.

Mizuno ST-G
$600 | Golf Galaxy
Hot List Gold

This low-spin head has two seven-gram weights that can slide in two heel and toe channels in the sole. The angled channels converge at the rear center of the sole and allow for an infinite range of heel- or toe-biased weighting. The channel cut into the front of the sole maximizes the way the face flexes. Also helping is a new titanium alloy that makes the face lighter, faster and stronger. The weight-saving carbon-composite crown and a steel bar in the channel’s polymer filling help to lower the center of gravity.

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1. A lighter, faster, stronger face. The new ST-G driver makes use of a new heat-treated Ti 412 alloy that is lighter density than the company’s SAT 2041 used in its recent ST-X 230 and ST-Z 230 drivers. That means the face is lighter, but the heat treatment makes it even stronger so it allows more potential face deflection for better ball speed across the face. The lighter, stronger alloy allows for a more intricate variable face thickness design.

“Because it’s lighter and stiffer, we can reduce some weight in the face to use elsewhere,” said David Llewellyn, Mizuno’s director of research and development. “But we’re also able to design it for better flexibility because we can make it thinner. You want that combination of higher strength with better elongation because it will stretch more before it breaks.”

Boosting the way the face flexes is an updated version of the company’s weighted, sole slot technology that debuted last year with the ST-X 230 and ST-Z 230 drivers. Known as the CORTECH Chamber, the slot is cut through the front of the sole to allow the face to give more at impact. The slot is filled with a thermoplastic urethane, which in turn is embedded with a four-gram stainless steel weight slug. That combination both allows the face to flex better while pushing the head’s center of gravity low and forward. That reduces spin for a more efficient launch and better distance.

“Yes, it’s a smaller head to make it more workabl.e, but that C.O.R. area is pretty large for this category of driver,” said Llewellyn. “By using a new face material and tweaking the CORTECH geometry, we’re able to get more stability and consistency for off-center hits.”


2. Less leads to more. The new ST-G, which is first and foremost positioned as a low-spin option in the Mizuno driver lineup, utilizes more carbon composite than in Mizuno’s past low-spin drivers by not only covering a wider area of the crown but also extending the carbon composite to wrap around the toe section of the sidewall. That helps to create a more neutral CG location (because taking weight out of the toe section balances the extra mass from the toe-side sliding weight). But it also allows for the two tracks on the sole for the sliding weights to angle to the extreme back of the sole where they converge at a central point.

That creates not only the option for greater heel and toe weighting like in the dual track system of the ST-G 200 driver but also the extreme rear weighting option of the ST-G 220. The two 7-gram weights can be pushed forward for an extreme but balanced low-spin setting, but they also are designed to produce a higher flight with the two weights positioned at the back of each of the converging dual tracks. The weights can be positioned in any combination of heel or toe bias and to provide a range of spin settings from low to mid-low. Internal ribbing within the head around the weight tracks is designed to improve the consistency of sound across all settings, particularly in the rear-most position.

3. A player’s shape. Make no mistake, the new ST-G driver targets that group of better players who prefer a compact, more workable head, what Llewellyn calls “a squattier profile.” It will check in at 440 cubic centimeters but also features a taller face and is designed to sit square at address. But unlike past versions the line now includes more than a 9.5-degree option, adding a 10.5-degree and a left-handed 9.5-degree as well. The addition of the 10.5 means the loft range on the adjustable loft heads stretches from 7.5 to 12.5 degrees. While adjustable, the standard lie angle on the ST-G is flatter than the ST 230 drivers to provide a more neutral flight, as well.