Sophie Walker

When a player as good as Brooks Koepka chooses to put your irons in the bag and starts winning major championships with them, you know you're doing something right.

The American has been using Mizuno's JPX Tour irons for the last few years, despite not having an equipment contract with the brand, simply because he feels that they are the best possible tools to help him perform.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The new JPX921 Hot Metal and Hot Metal Pro Irons aren't exactly aimed at players like Koepka, but certainly looking to help give the 'average golfer' the forgiveness and distance boost that they'd want in a package which looks and feels sleek and premium

What's It All About?

Mizuno say that the new Hot Metal and Hot Metal Pro irons deliver their fastest ever ball speeds, with a straight ball flight and 'controllable' landing angles.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

This is the third time that Hot Metal irons have used Chromoly, and Mizuno's R&D suggests that any new technology needs three iterations to achieve optimal performance, so these should be the best yet!

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The Seamless Cup Face has a variable thickness sole design, which allows the leading edge to act as a hinge and produces greater flex at impact, keeping up ball speeds on strikes that are down towards the bottom of the face.

The Hot Metal Pro version offers a slightly more compact profile, with a little less offset, whilst both iron models feature new complex face geometry to generate better energy from the clubface.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The heads are complete with a pearl brushed finish to minimise glare from the sunlight, although that is not always needed on dull days in Manchester! There is also a stability frame with extreme perimeter weighting towards the toe to aid off centre strikes, however this isn’t as much as previous models and weight can be moved to behind the hitting zone.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Compared to the MP-20 range, Mizuno are suggesting that you should see a straighter, higher ball flight and a slightly more forgiving head shape.

The Test

I took the Hot Metal and Hot Metal Pro irons to my simulator at Mercedes Benz, LSH Auto. I tested them using Trackman 4 and Titleist Pro V1x balls and gained club data with 9, 7 and 5 irons.

My aim was to conduct thorough testing in order to give my opinion on the speed, stability, forgiveness and looks of the JPX921 Hot Metal and Hot Metal Pro's. Could they be the ideal option for a mid-handicapper who wants the feel and prestige of a Mizuno iron without having to sacrifice any forgiveness?

Mizuno JPX921 Hot Metal and Hot Metal Pro Irons Review

Looks and Feel

Both the Hot Metal and Hot Metal Pro irons are made from the same Chromoly material but the Pro has a visibly shorter blade length, smaller sole and thinner top edge.

So essentially the Pro gives you the same technology but with the size is closer to that of the Forged model. However it still has the same lofts as the Hot Metal which are 2 degrees stronger than the Forged, and 5 degrees stronger than the JPX921 Tour. Are Mizuno finally succumbing to jacking up the lofts in their player's clubs?

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The Hot Metal Pro (left on above image) has a noticeably thinner top edge and less offset than the Hot Metal (right on above image), so maybe Mizuno is right, you don’t need chunkiness to still be forgiving?

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The Hot Metal really did get thick at the top end of the bag and I could see the bulk at the back of the 5 iron head. The sole thickness gradually increases from the short irons up to the longer irons, which I think is a fantastic idea as my attack angle also decreases as I make my way up to the bag.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

The brushed satin finish instead of polished chrome is a huge bonus in my eyes. There is a touch of shine on the back of the club but I cant’t see that at address so it doesn’t distract you at all - it's almost like a shiny football sticker of your favourite football club's badge.

As you'd probably expect, neither the Hot Metal or Hot Metal Pro irons feel quite as buttery soft as the Forged or Tour model, but I was still pretty impressed. They both feel 'hot' off the face too which is nice for me, as I struggle to generate lots of speed by myself so it's reassuring to think that the club is giving you a little bit of extra help.


Whilst testing these irons I really did flush the Hot Metal Pro Irons. The graphite Project X shafts really helped with this as they are similar to the Accra shafts I already use in my irons, so they made it easy to swing freely and at a decent speed.

I actually hit the smaller Hot Metal Pro a little further with the 9 iron, achieving 4 yards extra carry on average, and both heights were pretty similar so there was still that 'drop and stop' control that you want from a shorter scoring iron.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Similarly the numbers for both models with the 7 iron were very similar, and I was pleased to see that there was a nice bunching produced (particularly with the Pro) during testing. This is always a positive as you want to be able to trust your yardages out on the course.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Moving into the longer irons was where the larger profile of the Hot Metal started to show itself, and I actually found the Pro model much more playable in this instance.

I found it difficult to get the thicker sole under the ball with the Hot Metal and so the consistency of my strike and dispersion seemed to suffer as a result, with the ball flight coming out a little high and spinny.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Some of this may be due to the shaft I was using with the Hot Metal Pro, as it produced more than 1000rpm less spin and was carrying 167 yards with a 5 iron with a penetrating flight, which was almost 10 yards longer than the Hot Metal.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

As is often the case with these slightly chunkier, lower spinning irons you always have be wary of that 'rocket shot' which jumps out much further that the rest of your shots, and one of the shots with the Pro was up at 172 carry which is a slight worry as that is likely to go flying off the back of the green and into the trouble behind.

Whilst this may have just been a one-off it's something that you always have to be aware of when considering these 'players' performance' irons.

Sophie's Numbers

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Mizuno JPX921 Hot Metal and Hot Metal Pro Irons Verdict

I could certainly game the Hot Metal Pro’s through the bag at the moment, although if I was back to my tour days I think I would only use them in the longest irons for a little more help (as Kelsey MacDonald does, she has a Hot Metal Pro 2 iron). I'd still be a little worried about getting those fiery numbers which can be impossible to anticipate, although this may a price worth paying for more forgiveness and distance with the longer clubs.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

Despite this, the Hot Metal Pro still manages to present itself as a 'slimline' iron which actually made the Hot Metal look quite chunky - and I was surprised with the Hot Metal being more difficult to hit in the longer irons due to their more chunky profile.

The irons are stronger in loft than the Forged irons, but achieving 114mph average ball speed with a 5 iron really is good for me and also backs up Mizuno's promise that you're going to see an increase in this department.

I would pick the Pro model over the standard Hot Metal as I have worked out during my time testing golf clubs that if I like the look of a club down by the ball, it can really aid my strike, and in turn performance.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

I'd recommend the Hot Metal models as a long iron replacement for better golfers who are looking for a little bit of extra reassurance, or as a whole set for 15 handicappers and down.

Last year I tested the MP-20 HMB Irons and I'd say that these irons were better looking and the performance was a little more impressive too.

Mizuno JPX921 Hot Metal & Hot Metal Pro Irons

My only warning would be that the Pro model is lower in launch and spin than the standard Hot Metal, so make sure you're picking the right model for your game, but if you get that right then you should really enjoy using these shiny new bats from Mizuno.

Hot Metal Pros

  • Nice high launch
  • Spin rates were right where you'd want them
  • Good multi-compound grip

Hot Metal Cons

  • Head shape is quite large

Hot Metal Pro Pros

  • Looks great
  • Good forgiveness levels
  • Ball flight was penetrating

Hot Metal Pro Cons

  • Not available in left handed
  • Low spin levels
  • Standard grip could've been better

If you enjoyed this, you may also like:

Mizuno MP-20 HMB Irons Review

Titleist T100S Irons Review

Golfalot Rating: 5 stars
More from Mizuno


Mizuno JPX921 Hot Metal Iron

Mizuno JPX921 Hot Metal Irons - Product Details

UK Launch17 September 2020
UK Launch RRP£945
European Launch17 September 2020
European Launch RRP€1365
Handicap Range
Hand AvailabilityLeft, Right
DesignCavity Back
Set Makeup4, 5, 6, 7, 8, 9, PW
Additional ClubsGW
Manufacturer's WebsiteMizuno Website

User Reviews

Marshall Moyes
June 2021

Just purchased a set of Hot Metal pros following a proper fitting. Firstly I would say that your review of these clubs is spot on , extremely fair .
I am 74 yrs old and was beginning to lose some distance and I did not like the idea of going to a chunky game improver club. I was playing Srixon 745 forged irons which were about 6 years old.
By switching to the Hot Metal pros with Accra graphite shafts , I have regained distance ,roughly now one club less . The pro model is not a forged iron , or overly thin but it is still a good looking club and you would be hard pressed to feel that this was a cast club. Excellent choice , especially when your club speed is getting slower and you know that you are not going to get results with a tour iron . You want a players club but you need a little help.. I think Mizuno have done a great job .

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