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Mizuno JPX 921 Hot Metal Irons Review

Mizuno are well known for making irons with a classical design and great feel. However, the JPX Hot Metal range is their offering for golfers wanting something a little different – exceptional distance and forgiveness.

As you’ll see in this review of the JPX Hot Metal and Hot Metal Pro irons, there is more to this the JPX 921 range than just stronger lofts.

Buyers guide quick summary

  • Want a game improvement iron with a great feel and control – check out the Mizuno JPX 921 Hot Metal irons.
  • Want the look, feel and control of muscle back irons, but still want forgiveness – check out the JPX 921 Hot Metal Pro irons.

Mizuno JPX 921 Hot Metal irons

Mizuno JPX 921 Hot Metal 7-iron

The JPX 921 Hot Metal irons are Mizuno’s most forgiving and most powerful in the JPX line up. However, they are not exclusively designated for high-handicappers, rather golfers preferring a larger club head and great distance.


The JPX Hot Metal irons feature a thicker top line, wider sole and longer club head (heel to toe) compared to the rest of the JPX range. This being said, they are still quite refined compared to similar game improvement irons, such as the TaylorMade Sim Max irons.

The head lengths across the set are 5-7mm longer than the MP-HMB irons, making the Mizuno JPX Hot Metal your top choice if your looking for large, forgiving Mizuno irons.

Check out our Mizuno MP-20 review here


The larger head size combined with a stability frame placed behind the club face creates a high moment of inertia – which minimises twist on off-centre strikes. The result is exceptional levels of forgiveness and distance for heel and toe strikes.

The second result of the stability frame and ultra thin Chromoly face is a club head where the sweet spot is lower than in any other iron Mizuno have made. As a result, thinned shots will travel further and the ball will launch higher across the face for every club.

Power & distance

The changes above allowed Mizuno to reduce their standard irons lofts across the set (just by 1º), without losing any launch height or shot-stopping ability. The lower lofts produce a higher ball speed and greater distance.

The JPX 921 irons also feature a COR-TECH face that is now 0.2mm thinner across the centre compared to the JPX 919’s, resulting in even higher ball speeds. The face thickness also varies across the hitting surface to optimise ball speed from all areas of the club face.

The combined result is that these are the longest irons Mizuno have ever engineered.


Three new sound ribs have been added to the top line of the JPX club head to make it lighter, stiffer and to enhance acoustics. The result is a pure feel and a sound that is more like a muscle back iron than a game improvement club.

The JPX Hot Metal irons are cast, not forged, meaning they do feel different to the forged MP-20 irons. In terms of feel they sit some where between the Ping G410 and the MP-HMB irons. They feel great, super solid, but not quite as soft as the MP-20 forged range.

Control & shot-shaping

The Mizuno JPX 921 irons have the largest head size and most offset in Mizuno’s range. As with other Mizuno iron sets they feature a progressive design, whereby head length, sole width and offset reduce as you move from long irons to short irons. This gives you great forgiveness in the long irons and greater control in the short irons and wedges.

Where the JPX Hot Metal differ from other Mizuno irons is that the sole width stays much wider in the 6 and 7-iron and offset reduces considerably as you move into the 9-iron and pitching wedge. The result is a 6, 7 and 8-iron that really will provide exceptional forgiveness.

Mizuno JPX 921 Hot Metal – Golf Insider verdict

If you are looking for forgiving irons that offer great distance and feel then the Mizuno JPX 921 Hot Metal irons are an ideal choice. They offer game improvement performance in a much sleeker design.

Mizuno JPX 921 Hot Metal Pro irons

Mizuno JPX 921 Hot Metal Pro 7-iron

The JPX 921 Hot Metal Pro irons are Mizuno’s tweak on the Hot Metal irons for those players wanting great distance and forgiveness in a more compact head design.


The Hot Metal Pro irons have a slightly thinner top line and narrower sole compared to the standard JPX 921 Hot Metal irons. However, the standout difference, for me, is the reduced level of offset.

The head profile and level of offset are very similar to the Mizuno MP-20 MMC irons.


This head is smaller and slightly shorter than the standard Hot Metal iron. However, both forgiveness and distance for off-centre strikes are excellent. The variable face thickness and stability frame aim to get toe and heel strikes as close as possible to your target when shots miss the sweet spot.

The JPX 921 Hot Metal Pro irons are for golfers who are willing to lose a little forgiveness for a more classical looking iron.

Power & distance

The lofts and face technology are the same across the Hot Metal and Hot Metal Pro irons. Meaning these irons are still the joint longest irons Mizuno have created (along with the standard JPX 921 Hot Metal irons).

The tweak in club head design, and resulting change in centre of gravity, in the pro-version produces a slightly lower ball flight, but nothing that is too noticable.


Similar to the standard Hot Metal irons, these are cast, not forged. The smaller head does result in a sharper and crisper feeling when striking these irons out the sweet spot. However, they are noticeably different from the buttery, soft feel of the MP irons, but beautiful nevertheless.

Control & shot-shaping

The smaller, shorter club head, narrower sole and reduced offset all give the impression of an iron with more control and versatility. The iron heads sit well behind the ball and are adaptable to any lie.

In practice, the difference in control and shot shaping between JPX standard and pro irons is minimal. Both are pitched for distance and forgiveness over the playability of the MP-range. However, both offer far greater control and playability than comparable game improvement irons, such as the TaylorMade Sim-Max or Cleveland HB irons.

Mizuno JPX 921 Hot Metal Pro – Golf Insider verdict

If you are looking for a traditional looking irons that offers excellent distance and great forgiveness then the JPX 921 Hot Metal Pros are an excellent choice. Slightly higher launch and distance than the Mizuno MP-20 MMC’s but very comparable in terms of looks.

Should I buy the Mizuno Hot Metal JPX irons or JPX Pro irons?

Opt for the standard Hot Metals you struggle with distance and consistency in your long and mid irons. The increased head size, wider sole and offset will give you those extra few yards and tighter dispersion when hitting into the green.

If you are willing to give up a little forgiveness for a smaller looking iron then opt for the JPX Pro irons.

Mizuno MP-20 irons vs Mizuno JPX irons – what is the difference?

The MP and JPX ranges differ in their approach to design and ethos. At a simple level, the JPX are multi-piece irons focused on generating a higher ball speed and a straighter ball flight. Whereas, the MP-20 range are more classical in design, forged and focus on exceptional feel and greater workability.

The MP-20 range offer great control and the beautiful soft feel Mizuno irons are know for. The JPX range feel some where between a Ping/Callaway and a Mizuno forged iron.

Ping G410 & G425 vs Mizuno JPX 921 Hot Metal

Good question. In terms of design and performance, these are two very similar irons. We ran a full test comparing the Ping G425 and the Mizuno JPX irons, click here to check it out.

Check out a full review of the Ping G410 irons

Mizuno JPX 921 Hot Metal specs

Club #Loft °Lie AngleOffset (inch)Length (inch)
For full custom-fitting options see

Dexterity: RH and LH

Mizuno JPX 921 Hot Metal Pro specs

Club #Loft °Lie AngleOffset (inch)Length (inch)
For full custom-fitting options see

Dexterity: RH Only

Mizuno JPX 921 Hot Metal irons vs JPX 919 irons – What has changed?

The JPX 921 irons now feature an even thinner face, resulting in higher ball speed. The soleplate has also been tweaked to increase the face flex upon impact. The JPX 921 Hot Metal irons also feature new dampening bars to refine the feel and sound of the strike.

What does JPX stand for?

Japanese Performance Extreme – the JPX range were first released in Japan and the JPX tagline was used to push the new aggressive, distance-driven range of irons.

Mizuno JPX 921 Hot Metal iron review – Summary

Both the JPX 921 Hot Metal and Hot Metal Pro irons are a welcome addition to the market. They offer game improvement performance in two beautiful-looking clubs. You may also want to check out Mizuno’s latest Pro irons.

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Will Shaw, PhD, MSc, PGA Pro

Will is a PGA golf professional, with a PhD in Biomedical Science and MSc in Sports Biomechanics & Psychology. He spent 10 years lecturing part-time at Leeds Beckett University and the University of Leeds in Biomechanics and Motor Control before becoming the Head of Golf for the University of Exeter. He currently runs Golf Insider UK, Sport Science Insider around wider consulting and academic roles in sport performance and motor control.

1 thought on “Mizuno JPX 921 Hot Metal Irons Review”

  1. Hi Will,

    Thank you for this review of Mizuno JPX Hotmetal Irons. I have two sets, one in England and one in Ireland because I live in both countries and transporting clubs constantly is not practical. My best handicap was 5 but as I get older I find I need a little more help to maintain a tidy game. At 73 now, still single figures but only just, the distance I once relied on has had to be replaced with a steady straight game. I try to make less mistakes and putt economically. My Mizuno clubs fit my game perfectly. A high ball trajectory helps me stop the ball on greens – even if I have to hit more club to get there. Lastly, I find the clubs visually pleasing and maybe if they look good there is a confidence rub-off factor. I have found hitting a 7iron when once I hit a 9iron for the same shot does not induce a shame issue into my game – the fiver coming my way in the bar soon overcomes that slight regret I might privately have. Good luck with Golf Insider.


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