SingleLength Irons:
Products
Dave Tutelman 
August 19, 2007
Updated November 21, 2015
Updated November 12, 2016
Having established the principles
I intend to use in evaluating singlelength iron sets, this page is a
compendium of iron sets on the market, measured against those
principles.
Bear in mind that this study is done using computer modeling, based on
the published specifications of the clubs. I do not
have the resources to do a lot of testing with real clubs.
Summary
On this page, I have a brief description of each of the products on the
market that I have had a chance to analyze. Let me stress that I am
analyzing them based on their published specs and computer modeling. I
have not actually tested the clubs in the flesh. In evaluating range
and gaps, I am using the same golfer model that I used on the first
page of the article.
 The golfer has a clubhead
speed of 80.1 to 80.3 mph, based on the clubhead weight. (Since all the
models in late 2016 were in the low 270s of grams, the speed spread is
negligible.)
 The angle of attack is zero, and the
dynamic loft is exactly the same as the nominal loft of
the clubhead. The assumption is that
the novice golfer
is the most likely target for a singlelength set. Note:
 If you have forward shaft lean, you will tend to incur
more longiron droop.
 If you have a higher clubhead speed than 80mph with a
7iron, you will tend to incur less longiron droop.
 Since
most (not all, but most) better players have both shaft lean and higher
clubhead speed, the effects tend to oppose and to some extent
cancel each other out.
Let's start with a table that summarizes the descriptions. There is more detail, including a gap graph, in the descriptions
themselves. They are listed in roughly chronological order of their
appearance on the market.
Model 
Brand 
Set
Makeup 
Range
(yd)
[1] 
Gap
Shape
[2] 
Head
Weight
(grams) 
Lie
Angle 
Offset
(mm) 
Comments 
OneIron 
OneIron 
3i
 LW 
103
(196  93) 

273 
63.5° 
3.2 
Only
assembled clubs 
iMatch 
MyOstrich 
4i
 PW 
88
(190  102) 

272 
 
 
No
longer in business 
Pinhawk 
Value Golf* 
4i
 LW 
100
(193  93) 

272 
62.5° 
3 

Sterling 
Wishon* 
5i
 GW 
95
(191  96) 

274 
63° 
4
 2.5 
"Long"
irons are hiCOR
5hybrid available 
In1Zone 
Diamond Tour 
4hy
 SW 
91
(190  99) 

273 
63° 
3.2 
5
hybrid or 5 iron choice 
King F7 One 
Cobra 
3i
 GW 
101
(197  96) 

272 
62.5° 
5.5
 1 
"Long"
irons are hiCOR
Only assembled clubs 
King Forged One 
Cobra 
4i
 GW 
89
(185  96) 

275 
62.5° 
2
 1.3 
Only
assembled clubs 
iWin 
Integra 
5i
 LW 
87
(183  96) 

272 
62.3° 
6.6
 2.3 

 Range is from
the lowestloft club through the gap wedge. Sand and lob wedges are not
usually used as fullswing clubs (though they may be). Moreover, it is
common for SW and LW to be purchased separately, not part of the set of
irons. So I have removed the SW and LW from the comparison of range and gaps.
 My original
plan for the table was to boil down the gap shapes to flat, proportional, and
dysfunctional
(i.e.  antiproportional). In trying to classify the gap graphs, I realized that gap shapes are
a little a bit like clouds; different people may conclude
differently what they look like. So I'm putting a thumbnail
here
of the graph itself. I'll interpret the shape in the detailed section
on each iron.
But it is instructive to look at how the early entries
did a good job of flat gap (OneIron) or proportional gap
(iMatch and Pinhawk). Some of the later entries seem to have just
rushed in with a loft lineup they were familiar with, and wound up with
somewhat dysfunctional gaps.
Descriptions
The descriptions contain more detail than you can put in a table like
the one above. The most important part of each description (at least
for me, your mileage may vary) is the distance and especially gapping
information. It is the most significant difference from model to model,
in terms of what it can do for (or to) your game.
Each of the gap graphs shows the gap (the bold, red line) using the
assumptions discussed above (about 80mph clubhead speed and zero AoA). It
also has a plot of a perfectly flat gap lineup and a proportional gap,
each to give the same range the set of irons has.
One Iron
Golf
One Iron Golf has been in the
business of singlelength sets for years, long before it was
fashionable. They date back to the 1990s, and are mentioned in each of
my articles on the subject.
Look at how well their set tracks the constantgap ideal. Only two of
the eight gaps are more than one yard from the constantgap line.
The heads are modest cavityback designs, game improvement clubs but
not extreme. The shape and cosmetics are not current, more like 1520
years ago. They have a constant 3.2mm offset for all clubs.
The company only sells assembled sets of clubs, not components. They
custom build the clubs, where the parameters of customization are:
 Length, based on your wristtofloor measurement.
 Shaft flex, but only selected from TrueTemper steel
shafts. They don't say how they infer your proper shaft flex, nor which
TT steel shaft[s] they use. The words on their web site suggest they
align the spine, but I have never seen a TT steel shaft with a spine
big enough to bother aligning.
 Grip size: standard or 1/8" oversize.
The bottom line for me: if these heads were on the market as
components, I would be interested in them. I'm not crazy about
their fitting method; it only scratches the surface of what a real
clubfitter does. But it is still a lot better than buying off the rack.

iMatch
MyOstrich
golf is no longer in business, and the iMatch model is not
available. I couldn't even find one used on eBay.
So this is included only for historical interest. That, and the very
nice approximation to a proportional gap lineup. Except for one gap of
droop at the lowloft end (which we understand and sort of expect),
this does very well at proportional gapping. It tracks the dotted green
curve (the ideal proortional gap) rather well.
At the time the iMatch was being designed (20082010 IIRC), I was
working with Tim Hewitt, the architect of iMatch, on another project. I
had occasion to discuss iMatch with him, and he took a real systems
approach to the set. He did not feel constrained by what "the market"
was doing, and went for larger loft gaps at lower lofts  which is
exactly why this gap graph is so attractive.

Pinhawk
Pinhawk was introduced by Value Golf, and is now sold by Hireko as well. Its loft lineup is
very similar to the iMatch (5° loft gaps at the lowloft end and 4°
loft gaps at the highloft end). As a result, the gap graph is very
similar to the iMatch. It does a good job of tracking proportional
gapping, except for one drooping gap at the lowloft end and one gap a
couple of yards high between PW and GW. All in all, a wellexecuted
architecture.
The heads have a modern gameimprovement cavity. The offset is a
constant 3mm. If I were building a set for myself or a friend, my
search would certainly begin here  and likely end here as well.

Sterling
The Sterling singlelength irons were
a joint project of Jaacob Bowden and Tom Wishon. Bowden heads up the
Sterling brand, which sells assembled clubs customfitted. There is no
indication on the site how the fitting is done, so I have no comment on
the quality of fit. Wishon retired from the component business soon
after the Sterlings were complete. He sold his brand and products to
English component supplier Diamond Golf International. So it will be up
to them whether and how to offer the Sterling heads.
As with many Wishon designs, there is some innovative technology
involved to make it work. He also chose a 4°/5° loft split, like iMatch
and Pinhawk. But unlike those predecessors, he put the 4° at the
lowloft end. At first look, I thought the gap pattern would be a dysfunctional
distaster. But Tom did something pretty clever; he put highCOR ("hot")
faces on the 5 through 7irons, giving them about five more yards of
distance. This "preaccelerates" them, so they are already somewhat
compensated for lowiron droop. The resulting gap graph looks a little
humped, but it never wanders very far from a flat gap. Very clever, and
effective.
Jaacob
Bowden sent me some corrections too late to make it into the
calculations. I hope to include them in the next iteration of this
article. In the meantime, here are some of the things I'll have to
address next time:
 The hot faces are .83 COR, rather than
the .82 I used in my modeling. That will probably increase the 8gap by
less than a yard, and the same for the range.
 They have introduced a 4iron (but not a 4hybrid).

I went ahead and plotted what the gap shape would
look like if all the Sterling irons were a simple cast face, not a thin
flexible face. The resulting graph shows a 5yard discontinuity between
the 78 gap and the 89 gap. Those two gaps are identical for the real
Sterling irons, which contributes to the flatness of the overall shape.
And it is explained completely by the fact that the 7iron is the
"longest" club in the set with a hot face. So that bit of technology
works superbly.
The head itself looks closer to a blade than a game improvement club;
the cavity is pretty shallow. But there is a lot of weight down low, so
it should be easy to get the ball airborne. The offset is progressive,
but a very mild progression from 4mm to 2.5mm.
A few attractive and unusual features of the product:
 You can replace the 5iron with a 5hybrid matched to
the rest of the set.
 The bodies of the irons are soft carbon steel, so
customization by bending is easy, and over a greater range than other
singlelength irons (which are cast 431 stainless steel  still
bendable, but not as easily, or over as great a range). Of course, the highCOR faces are
not carbon steel, but they don't have to be.

In1Zone
Diamond Tour Golf, a supplier I often do business
with, introduced a singlelength set. They call it In1Zone, consistent with the
InAZone brand they use for other recent clubheads. Since I like many of
their products, I looked forward to this. Sorry to say, I was
disappointed.
The loft lineup they chose is the same "modern" loft lineup they use
for their conventionallength irons. And that lineup is the result of
the Loft Wars,
with the smallest loft gaps for the lowestloft clubs. As you would expect,
the result is a dysfunctional gap shape, with the "long" irons having
less than half the gap of the "short"irons.
The heads themselves are attractive, and I'm sure they are competent;
Diamond Tour would do no less. They look like modern game improvement
clubs, and have a constant offset just over 3mm. The #4 is a hybrid,
and you have a choice of hybrid or iron for #5. If the gaps were
reasonable rather than dysfunctional, I would consider them
a contender for "best in show".
(Added
Mar 1, 2017) I just received an email from Roger White, who tells me
that the In1Zone clubs are very easy to bend, especially considering
they are cast stainless steel. While he agrees that the gap lineup is
dysfunctional off the shelf, it is not hard to fix. He now has a set
consisting of 5iron through sand wedge, which he has bent to 5° loft
increments from 20° to 55°. That required a bend of 4°, a bend of 3°,
and all the other bends 2° or less. His report of distances suggests a
very workable gapping between 10 and 15 yards. There is still a slight
tendency towards droop; the 56 iron gap is 10 and both wedge gaps are
15. But that is still a substantial improvement on the way the clubs
come from the manufacturer.

Cobra
King F7 One
In the Fall of 2016, Cobra announced that they would
be making the new singlelength irons for Bryson DeChambeau, and that
they would be a regular product offering as well.
Unfortunately, there were no specs on the Cobra site, just hype. It
took the MyGolfSpy.com site to post
information useful for analysis. But there was enough information there
to start, and here are my conclusions.
I didn't expect much from the set once I saw the loft lineup. The loft
gaps, starting at the 3iron and working toward the gap wedge, are
3345555. That sounds like a prescription for a dysfunctional gap
shape. When I did the work of computing the distances, the shape was
peaked, with a very sharp maximum gap between the 7 and 8irons. To
the right of that (all those 5° loft gaps), it follows a very nice
proportional shape. But as soon as you get into the less lofted irons
also having smaller loft gaps, the distance gaps drop like a rock. We
have four clubs worth of droop, not just one.
BTW, this happens even though the 4iron through 7iron have flex
faces, increasing the ball speed. The longiron droop would be even
worse without it. The problem arises
from the consequences of the loft wars coming home to
roost.
Will they sell? If the singlelength irons have a significant market,
they should sell very well. We have only one bigname OEM in the
market, and an interesting pro using and endorsing them. They look
good, and the range is a creditable 101 yards. And let's not forget
that the OEMs have been selling conventionallength irons with
dysfunctional gaps for over a decade; people don't seem to know nor
care. So yes, they probably will sell.

Cobra
King Forged One
On the same page at MyGolfSpy.com
is the club that
DeChambeau is more likely to be using  if he is using a generally
available product at
all (and not something completely custom). Cobra seems not to be making
as much noise about the Forged One club, but it is also a singlelength
offering.
It's
shape is closer to flat than peaked. That might be guessed by the loft
lineup. The loft gaps are 3344445; that would suggest a serious
longiron droop (and there is), but flatter across the rest of the set
(and it is). Of course, that gives a more modest range of 89 yards. Of
course, given that it is a forged "players' club", we might expect the
golfer to have more clubhead speed  so neither the droop nor the
reduced range would be as much of a problem. A strong player with lots
of clubhead speed might experience a relatively flat gap, not at all a
bad thing.
If you need any
further evidence that the Forged One and the F7 One are for different
markets (player's vs game improvement) you need only look at the
offsets. The F7 One has the largest offset progression of any
singlelength set I evaluated in 2016, going from 5.5mm for the 3iron
to 1mm for the gap wedge. Compare this with the Forged One, where the
offset is much smaller, and only progresses from 2mm to 1.3mm over the
whole set.

iWin
Integra is now in the game. They are a respected component company; I
know from experience that their products are of good quality. They
are available through Value Golf, the company that brought you the Pinhawk singlelength irons as well.
Unfortunately,
the iWin suffers from the loft wars  not as much as some other set
perhaps, but the longiron gaps are still 2° less than the shortiron
gaps. (Their pattern is 33.54.5555.) The result is a peaked gap
curve, with a proportional gap below the 8i and dysfunctional gaps from
5iron to 8iron.
The
offsets are very progressive (6.6mm to
2.3mm), indicating a gameimprovement target market. That is even moe
than intuition might say, because the set begins at the 5iron. Given
that the set has
only seven clubs, the range of 87 yards is not bad.

Mathematical and
computer model
As usual, the technical details are only interesting if you are
interested. If you're not, you shouldn't lose any understanding of the
results by not reading this. Obtaining distance from impact parametersThis part is relatively easy. I used Max Dupilka's Traj30 program
to compute the trajectory. It takes impact parameters and gives a lot
of output about the ball flight. The only output I used was the carry
distance. The inputs were:  Clubhead speed:
see below for how this was determined. But it doesn't much matter. The
clubhead speed model gave only a 0.3mph range  from 80.0 to 80.3 
over all the clubs considered. So the effect was negligible.
 Clubhead mass was taken directly from the specs for the club.
 Loft was taken directly from the specs for the club. (Remember our assumptions of zero AoA and shaft lean.)
 COR was taken to be .77 for most of the clubs. Where a "hot" face was involved, I took a guess based on how insistent was
the advertising about ball speed. There were only two such models, and
even then only for the less lofted clubs. I used .82 for the Sterling
and .80 for the Cobra F7 One.
Perhaps total distance would
have been better than carry distance, but I don't have a program that
can give total distance. Actually, it is hard to compute  starting
with the fact that it is strongly dependent on the characteristics of
the ground where the ball lands. The runout can be very different for a
hard fairway and a soft green. Then
again, there is an argument that carry distance is the proper measure.
Most iron shots carry a strategy based on where the ball lands.
Usually, when an iron is used, the goal is to land the ball at a
particular spot on the green. So one could argue that carry distance is
exactly the right measure. A word about the choice of program:
Traj30 gives pretty accurate results for irons. I'd have preferred to
use TrajectoWare Drive, but we are still in the experimental stage when
it comes to spins higher than 4000rpm. It is fine for driver
(and maybe some long irons), but we don't trust the distance numbers
yet for short irons. Late word in!
I am having trouble with Traj30 on my computer. I have finished all the
calculations, but if I have to go back and redo any  or evaluate a
new market offering  I may need to find a different program and
rerun everything with it. I hope that does not come to pass. Finding the clubhead speedIn
order to have comparable results, I wanted to apply the same swing to
each club in the study. This could have been done by making all the
clubs exactly the same length and using the SwingPerfect
computer program to simulate the swing. But I didn't want to manually
enter the data for every swing. (With 20:20 hindsight, that might have
worked for the singlelength sets; it would only need to be computed
once for each set, since the head weight is the same across the set.)
So I did things in two stages:  Given a head weight, find the
length that will give the same heft measure for the club. This was
done, and the length was sufficiently insensitive to small weight
variations that it came out 37.5" for all the clubs within one
decimal point. So I won't go into any more detail about how I did it.
 Use
SwingPerfect to find how clubhead speed varies over the relevant weight
and length, then come up with a simple formula that approximates it
well. We are talking about a very small range of weight and length.
Let's look at this  even though the total clubhead speed range was
only 0.3mph for the range of interest. (I want this "on record" in case
I need to do something like this again.)
My approach was to
find a set of swing parameters for SwingPerfect (things like torque
profiles and initial angles) that gave the results we were seeing on
the first page of the study. Those turned out to be: 40 footpounds of
arm torque, zero wrist torque, 170° shoulder angle, and 90° wrist cock. Then
I set up a table of head weights and lengths. The weights were 265g to
280g in 5g increments. The lengths were 36" to 38" in halfinch
increments. I used SwingPerfect to populate the table with clubhead
speeds. Here is the table, imported directly from Excel.
Speeds from SwingPerfect 

Head Weight (grams) 
Length (inches) 
265 
270 
275 
280 
36 
80 
79.5 
79 
78.7 
36.5 
80.3 
79.8 
79.3 
78.9 
37 
80.7 
80.2 
79.7 
79.2 
37.5 
81 
80.5 
80 
79.5 
38 
81.2 
80.7 
80.2 
79.8 
Just by eyeball, we can see that clubhead speed changes by::  Almost exactly a half mph per 5 grams of head weight, which is 1/10mph per gram.
 Almost exactly a third of a mph per half inch of length, which is 2/3mph per inch.
Writing this algebraically, starting from the topleft cell in the table: Speed = 80  1/10(weight  265) + 2/3(length  36) Here
is the table filled out with the SwingPerfect speeds (assumed to be
correct), the algebraic approximation, and the error between them.

From SwingPerfect 
Approximate formula 
Error 
Length (inches) 
265 
270 
275 
280 
265 
270 
275 
280 
265 
270 
275 
280 
36 
80 
79.5 
79 
78.7 
80.00 
79.50 
79.00 
78.50 
0.00 
0.00 
0.00 
0.20 
36.5 
80.3 
79.8 
79.3 
78.9 
80.33 
79.83 
79.33 
78.83 
0.03 
0.03 
0.03 
0.07 
37 
80.7 
80.2 
79.7 
79.2 
80.67 
80.17 
79.67 
79.17 
0.03 
0.03 
0.03 
0.03 
37.5 
81 
80.5 
80 
79.5 
81.00 
80.50 
80.00 
79.50 
0.00 
0.00 
0.00 
0.00 
38 
81.2 
80.7 
80.2 
79.8 
81.33 
80.83 
80.33 
79.83 
0.13 
0.13 
0.13 
0.03 
As
you can see any error is less than a tenth of a mph for most of the
range in question. Certainly a useful formula for our purposes.
Last modified  12/17/2016
