Project X IO Shaft Review

50 Words or Less

The Project X IO iron shafts are “Individually Optimized” to specific weights and trajectories for each flex.  Much smoother and more active than standard Project X.  Easy to elevate in the long irons.


Every golfer who’s into gear has certain brands that tend to work well for them and others that don’t.  While having these biases is natural, it can cause us to miss some great products.  I’ve never had great success with Project X iron shafts, but I tried to approach the new IO shafts with an open mind, and I’m glad I did.


There’s not too much to say about a steel shaft’s looks, but I do like the brushed chrome finish of the Project X IO shafts.  As is their custom, Project X made the IO stepless which adds to the visual appeal.  The branding is screened onto the shaft, so you don’t have to worry about a sticker getting wrinkled.


If you find someone who doesn’t like the original Project X iron shafts, chances are good that it’s because of the harsh feel.  The feel of the new Project X IO is a 180 degree change from that.  During the transition, the shaft loads smoothly and easily.  In the downswing, there’s a tight, controlled release of energy into the ball.  This feel is more prominent in the long irons; the short irons are less active.


Project X bills the new IO shafts as mid trajectory and mid spin which is exactly what I saw in my testing.  The active feel had me thinking they might border on high launching, but I found that their default was an ideal launch with enough spin to hold a green.

For longtime Project X fans, these shafts still offer plenty of control.  I found that it was easy to flight the ball higher or lower.  Though there was enough spin to hold a green, I observed that the spin was low enough to keep shot shapes quite small.  Unless I made an intentionally extreme (or unintentionally poor) swing, there were no slices or hooks.

The Project X IO shafts are available in 5.5, 6.0, and 6.5 flex, which translates roughly to regular, stiff, and X-flex.  As you move up in flex, the shafts get 5 grams heavier, starting at 105 grams in the 5.5.


If you haven’t tried a Project X iron shaft in a while, visit your fitter to check out the new Project X IO.  These shafts are lighter than your typical Tour-style shafts with substantially smoother, more active feel.  They’re a great middle ground for players that want control but don’t want to swing a telephone pole.

Visit Project X Golf HERE

Matt Saternus
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  1. How does this compare to the LZ?

  2. I was disappointed in these shafts although it was brief testing. I went from playing regular PX 6.5 and personally like the feel. After a fitting we realized I was leaving some distance and speed on the table which led me to being fit in Project X PXi 6.5. Ive played PXi the past 2 years but unfortunately theyre discontinued and the IO is supposed to be the “replacement”…. Maybe its familiarity with the PXi but head to head the PXi gave me 3mph more ball speed than the IO. Even the c-taper lite 115x gave me more ball speed but slightly higher launch

    I definitely agree I love the looks of the IO. I really really hope it was just an off day bc I like the looks so much

  3. How would you say these stack up against the AMT range?

  4. Dennis Lathouwers

    Hi Matt,
    If you compare this shaft with the Nippon NS Pro950GH Neo shaft, which one do you prefer? What’s your opinion about these 2 shafts?
    Because i’m really doubting which of those 2 shafts to purchase. So i really like to hear your opinion about it. Thanks.

    • Matt Saternus


      The Project X IO and Nippon 950 neo are vastly different in terms of weight and profile. If you’re between these two I would strongly recommend going and testing them both in a fitting.


  5. Glenn Tamagawa

    I’ve read many articles on the IO shafts and found conflicting information about the stiffness. One article mentioned the flexes are on the soft side, ex. 5.5 is a 5.0 and so on. Is that true?

    • Matt Saternus


      The IO feels much softer/more active than the standard PX, but I would not say it’s weak to flex. I think it’s probably more accurate to say something along the lines of “a PX player and an IO player are just different golfers and shouldn’t try to swap shafts.”



    • Hi Matt
      I’m considering project x 10 or the modus 105
      You’ve reviewed both as good shafts if your looking for less weight but which shaft do you prefer and why

      • Matt Saternus


        I prefer the Modus as it feels better to me and the profile fits what I want.



        • Dave Murdza

          Good morning Matt,

          Back to your last answer…I play and like modus 105 but sometimes feel the stiff flex can get away from me at times.

          Do you feel the io might play a little stiffer and would 5.5 be comparable to modus stiff?

          Appreciate your insight.

  6. Glenn Tamagawa

    Thanks Matt!

    Would you know if soft stepping the IO 6.0 will change the shaft flex from mid to mid-high like the 5.5? Just for comparison I currently play XP105 s300 soft stepped in MP4 irons. I like the feel and flight it gives. Looking to change shafts in the Apex TCB heads.

    • Matt Saternus


      My understanding is that soft stepping gets you an in between flex, so something like a 5.75. How that would affect your ball flight is something no one could know definitively, unfortunately.



    • As a former low-mid handicapper who took a twenty year hiatus from golf, I am astonished by the feel and workability of these shafts (110g 6.0 with Mizuno 225, 5-Gw). Whether it be an easy swing or swinging for the fences, I can feel it load and can easily transition through all shot shapes. I’m just getting back into the game, and these shafts have me excited to quickly surpass my decades-old capabilities. As Matt frequently responds. Nothing is more informative than a proper fitting. I almost went with the 115g’s but decided the 110’s will serve me better as a 45 y/o “new” old player. I love them and the 225’s.

      My OLD irons are copper ISI’s, and while I’m not trying to blow the cover off the ball, I’m easily 15yards over my Smithsonian Pings and can’t believe the workability… I tried every other comparable shaft in my fittings and am solidly confident I made the right choice.

  7. Hi Matt
    Thanks for the insight and great review. Any comparison between this shaft and the KBS C-Taper light?

    • Matt Saternus

      I’ve never tested them head to head, so I couldn’t add anything beyond what’s in my review:


    • Just from ready this article and having played the KBS C-Taper lite for the past two years. These sound almost identical! Although KBS states high-mid launch with low spin, they share the same characteristics from reading the article. You would have to add attack angle into the equation too.

    • After playing Titleist Gold DCI irons for the past 30 years (with extra stiff shafts) I was recently fitted and ended up purchasing the Ping I 525 irons with ProjectX IO 6.0 Shafts. Any thoughts on this combo?

  8. Is this shaft flex 6.0 equivalent to Project X PXI 6.0?

    I have the 6.0 PXI’s now which I like but was debating on moving up to 6.5 IO’s for new irons.

    Did you sample the 6.0 or 6.5’s? My driver swing speed is around 108mph which i use X flex for that.

    • Matt Saternus


      I tested the 6.0 that’s shown in the photos. I never spent enough time with the PXi to be able to make an informed comparison between the two.



  9. HI Matt,
    Great review. I am at a point that I ma trying out a few shaft/head combos for my next set of irons. Currently play, and love, the performance and feel of my KBS Tour 120s shafts. These IO shafts seem similar on paper, can you speak to the feel at impact as compared to the KBS 120s?

    • Matt Saternus


      It’s been a while since I’ve played any KBS outside of the C-Taper Lite, so I’d be hesitant to offer any kind of definitive comparison.



      • I am aging KBS tour V 110 stiff, Callaway can’t get th for much new irons but the recommendation is the Projext x IO 110 s based on weight I guess. Any advice before I spend 2k on new clubs?

  10. which level of stiffness is comparable to the dynamic gold 105 s300? 5.5 or 6.0?

  11. Great review Matt!

    If you were to pick between LZ and IO which one would you prefer? And why so?


    • Matt Saternus


      Personally, I would opt for the IO because it’s less active.



      • Is the project X 10 5.5 comparable to KBS taper light 95 . Can I really feel the weight difference? Otherwise how does the flight compare

        • Matt Saternus


          Yes, I think that’s a substantial weight difference that you will feel, so, no, I don’t think they’re comparable.



  12. Any insight or comparison between this and the KBS Tour? I was fit into KBS Tour 120 stiff iron shafts but have been struggling with my long irons. 6-PW they feel great but feel boardy in my 4 & 5 iron. I tried Project X IO in a 4 iron in the past and felt like it was easier to get through my swing.

    • Matt Saternus


      I don’t have any specific thoughts on that comparison, no. I’m a little surprised you found the IO to feel friendlier, but that’s why we always push fitting.



  13. What would be an alternative to PX IO 6.5

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