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Options for Flat Replacement Insoles for Running Shoes: Inov-8 and Ortholite Fusion

I’m a big fan of swapping insoles around between shoes. Sometimes a shoe might fit a tad tight, and swapping in a thinner insole from another shoe can free up enough space to make the fit comfortable. Sometimes a shoe is too cushy or too firm, and an insole change can completely change the feel for the better.

A perfect example of where swapping insoles saved a shoe for me was the Newton Energy. The included insole was too thick under the heel, and my heel would not lock down properly as a result. The insole was also too soft – overkill in a shoe with an already soft midsole. Swapping out the factory insole for a thin, light alternative turned the Energy from a shoe I’d hesitate to run much in to one of my favorite shoes of 2013.

As a shoe reviewer, swapping insoles is easy for me since I have a bunch to choose from. However, I’ve been asked a number of times about where to buy a thin, flat insole to use for this purpose, and it has been surprisingly difficult to find good options. Most replacement insoles for sale are heavily structured with thick cushioning and pronounced arch support – not ideal when the goal might actually be to increase space inside a shoe. Running on a bare footbed with the insole removed is an option, but the footbed can sometimes be rough or have exposed stitching.

After a bit of digging around, and a trial offer from an insole manufacturer, I’ve come up with a few options that are decent.

Inov-8 Replacement Insoles

Inov-8 sells insoles that are completely flat, firm, and have no arch support (the insole does curl up a bit on each side, but that is to assist with placement in the shoe I think). The insoles come in two thicknesses: 3mm and 6mm. I purchase pairs of both and measure the 3mm version to be 3mm in the forefoot, 4mm in the heel. The 6mm seems to be uniform thickness at heel and forefoot. For comparative purposes, the included insole in the Saucony Mirage 4 measures about 5.5mm heel, 4mm forefoot, and that in the Brooks PureFlow 3 is a uniform 5.5mm from front to back.

The 3mm insole appears very similar to the insole in the popular Inov-8 F-Lite 195 shoe (gray insole in photo below). Shape is also similar enough to the Saucony Mirage and Brooks PureFlow insoles that they swap into those shoes without a problem.

Inov-8 Insoles

Left-to-Right: Inov-8 3mm Footbed, Inov-8 F-Lite 195 insole, Saucony Mirage 4 insole, Brooks PureFlow 3 insole, Inov-8 6mm Footbed

Inov-8 3mm 6mm Footbed Comparison

Top-to-Bottom: Inov-8 3mm Footbed, Inov-8 6mm Footbed, Saucony Mirage 4 insole, Brooks PureFlow 3 insole

The Inov-8 insoles are available for $10 at Zappos in the US. I’ve had a hard time tracking them down outside the US. Amazon UK has them (seems Amazon US does not), so you might check the Amazon shop for your country.

Ortholite Fusion Insole

If you’re looking for a relatively thin, flat insole that has a bit more cush, the Ortholite Fusion might be worth a shot (Disclosure: Ortholite sent me a free pair to try out). Ortholite makes insoles for a lot of shoes on the market, you may even have a pair yourself. It’s a much softer insole than the Inov-8 models – almost has a memory-foam like feel to it. I measure the Fusion between 4.5-5.0 mm at both the heel and forefoot (hard to get it exact since it’s really soft). In the image below they look a bit thicker than the Inov-8 6mm insole, but I think they thicken a bit along the margins where I trimmed them.

Unlike the Inov-8 footbeds, the Ortholites have a bit of soft arch support built in, but it’s not terribly obtrusive given how soft and flexible they are.

Ortholite Fusion Insole Comparison

Left-to-Right: Inov-8 6mm Footbed, Inov-8 3mm Footbed, Ortholite Fusion Insole

Ortholite Fusion Insole Comparison

Top-to-Bottom: Inov-8 3mm Footbed, Inov-8 6mm Footbed, Ortholite Fusion Insole

The Ortholite insoles do seem to have a bit more girth, and they take up a bit more space inside a shoe, but if you have a shoe that runs like a brick with the included insole they may make things a bit more runable. You also have to cut them to fit your shoes so you can remove as much material as necessary to squeeze them in. I simply used an existing insole as a template and traced around it, then cut the margins off to make the Ortholite the same size and shape.

The Ortholite Fusion insoles are available in the US for $20 per pair at Amazon via Ortholite. I’m not sure why they’ve opted to sell this way, but you have to select a size on Amazon, then click on where it says “Available from these sellers” to purchase direct from Ortholite.

Other Options

Merrell sells an insole that comes in 3 thicknesses: 7mm, 5mm, 2mm. I have not tried them myself, but seems like it might be another decent option.

I’ve been trying to get Skechers to sell their insoles separate from their shoes – I swap Skechers insoles around frequently. Some people have had bunching issues with the thinner Skechers insoles, but has not been a problem for me.

If you have any other suggestions, please share in the comments!

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About Peter Larson

This post was authored by Peter Larson. Pete is a biology teacher, track/soccer coach, and dad (x3) with a passion for running, soccer, and science. If you'd like to learn a little bit more about who I am and what I do, click here, or visit


  1. I like the look of the Inov-8 3mm insoles. That looks like a real possibility.

    I may be wrong but I think that the Merrell insoles are made by Ortholite. I have called them before and asked if they had a zero drop insole for sale and a CS rep told me that they didn’t.

    I have also called Skechers to ask them to sell me a separate replacement insole and they said that they didn’t do that.

    • They have a few different models. One is Ortholite, the one I linked is something else. No sure if any are flat or not. Quite possible the CS rep had no idea what you were talking about :)

      • Trail Running Dad says:

        I’ve got a pair of the Merrell insoles Pete linked to in the article – they’ve worked pretty well for me, and seem flat (sorry, no calipers on hand to test it!), though there’s definitely a bit of a heel cup and curve in the arch. I use them in the Merrell ProTerras, to replace the stock insoles (4 or 5mm). As I’ve got a narrower foot, I use the 7mm insoles to take up a bit more volume, and the fit is much improved.

        Only limitation is that the insoles are designed for the last of more traditional Merrell shoes – thus, the insoles are a bit narrow in the forefoot relative to the shape of the shoes in their M-Connect/Barefoot line. They’re still pretty good for me, but would be best in shoes with medium/narrow-width forefeet.

  2. Hi Pete!
    Great post and great timing for me. One question, do you know if there are any “neutral” insoles with built in 4 mm drop?

  3. i’m glad to know that i’m not the only one who’s eager to tinker with insoles once i get the shoes home!

    i’ve swapped around my skechers insoles all over the place. right now i don’t believe that i have a single pair of shoes with the original insoles in them.

  4. An old yoga mat makes great insoles.

  5. Mike Graber says:

    6 mm is one-quarter inch thick. Is the Inov-8 really that thick? That seems like a lot. The 3 mm and 6 mm insoles don’t seem that different in the pictures. ??

  6. Hi Peter,

    Have you tried using sheets of PU foam or even Poron? You can get it in various thicknesses for pretty cheap (cheaper than buying insoles…), it lasts a long time, and has a good cush feel without being too soft. We’ve even seen some performance advantages with these in testing…

    Just an idea for you to try!

  7. Christian J. Carlo says:

    I have a pair of Saucony Virratas and they fit me great but I have a little bit of slippage on the heel. I think that a new thick insole would work for me but I don’t want to have an excess of cushioning, as the cushion on the Virratas are enough for me. Would a 7mm Merrell Insole work for me, or a thinner one?

  8. Do you have a recommended insole for extra cushioning? I love the fit of my Altra Instinct 1.5’s, but I develop a little bit of knee pain when I wear them for longer runs (14+ miles). I’m thinking a softer insole might be worth experimenting with before I relegate them to a different role.

    • The ortholites in this post are pretty soft. Only problem is I’m not sure how they’d fit in a shoe like the Altras since the toebox is unusually shaped.

      • Thanks. And yeah, the shape of the toebox is a bit of a concern of mine. It’s what makes the shoe great for me, but it makes something like this a bit challenging. I could always try buying a larger size insole and cutting it to shape/size.

  9. Hi Pete,
    Did you ever try out the Inov-8 3mm insoles in the Newton Energy? I’m curious as to how they fit. (Did they need to be trimmed, did they address the heal lift, etc.)

    – Bill

  10. Alex Stringer says:

    Hi Pete!
    I just picked up some Brooks Pure Flows from REI for super cheap, and haven’t gotten them in the mail yet to even try them out. I read your review of them and this page. I can’t pick up brooks insoles separate from their shoes, so the Pure Connect trick is out. Any suggestions? I would like a zero drop, but my concern is the wider toe box fit with a standard insole.

    • Which version Flow did you get? I think with the original I had no problem with the included insole, it was just the original Connect that gave me trouble. The new Flows don’t fit me well, need to try a thinner insole in them. I suspect the inov-8 will work but have not tried it yet.

  11. Any idea what the so-called ‘strengthening’ 3mm insoles that Altra uses in some of their shoes – are made from? Altra is discontinuing the 3mm insoles.

  12. Tammy Suire says:

    Skechers is not even putting the insoles in their shoes anymore! I ordered the identical pair that I had before and it came in without the insole! Doesn’t even feel like the same shoe! I checked in a store the same shoe and it didn’t have insole either

  13. I have recently discovered an unearthed gem through this YouTube video-, these are new artificial cartilage foam insoles that use Nano Technology in the foam to absorb the shocks before they reach your body. After using them for a while, I can tell you that they have worked like miracle for me and I’d advise you to go and check them yourself at; they also have an online web store.

    • Have you been using the basic 5mm Artilage insoles? I’m just asking because I see they offer two more expensive versions (Dynamic Arch and Instant Custom Orthotics). In what running shoes have you used these Artilage inserts?

  14. I have a pair of Nike Free 5.0 that are missing the insoles. I have orthopeadic insoles that I usually use, but ive been told that this shoes should not be used with orthopeadic insoles. Can anyone recommend some insoles? I will be using them for walking, not running.


  15. I have recently discovered I have plantar fasciitis and need to wear zero drop shoes, which I have. I’m nervous about wearing my black leather boots I love to wear in fall and winter. They are pretty flat but are not “zero drop.” I was hoping I could find an insole that might turn a regular pair of shoes/boots into “zero drop.” Is that possible?

    • Hmm…depends on how much heel lift there is and how much room there is up front to add some cushion under the forefoot. Have you found that zero drop is helping you PF?

      • Peter, yes, zero drop shoes give no NO heel pain! I’m a believer. My boots have a 3/4″ heel, and there is room for an orthotic inside. But I don’t think there is enough room to raise the forefoot enough. I would LOVE it if a good shoe company would come up with a zero drop version of a few styles of shoes and boots.

  16. Peter, have you by chance measured the ortholites that come in the Hoka’s? I swapped out my Bondi 2 insole into my Newton Motion III’s and was amazed how much different/better the shoe felt and fit. Newton makes some pretty great shoes, but as you stated… the heel cup is think and odd shaped and for me I have a higher volume foot, so Newton insoles are annoying to me. Newton suggested I remove them, which works, but it’s not smooth riding as the footbed is ‘grippy’.

  17. Imre Nagy says:

    Just a little addition. It seems that Zappos and Amazon UK only have the Inov-8 insoles in 3mm option. I found that Pete Bland Sports in the UK ( has both the 3mm and 6mm version in two colors. They ship worldwide.

  18. Suzanne says:

    I have been searching for a Skechers goga mat replacement insole ever since the product was introduced. Unfortunately they do not sell them separately. Why I do not understand. They sell a shoe, then 6 months later sell the same shoe with a different insole. Why do I have to buy the same shoe all over again to obtain the product I would love? I’m frustrated with Skechers and hope they do something about it soon.

  19. Hi Peter,
    Nice post! Do you have any experience/ advice for running with an insole with great arch support? I’m trying to weigh the pros/cons – i’ve heard arguments on both sides.
    What do you think?

    • I have not, I tend to avoid adding anything supportive inside the shoe. That being said, if they feel good, I see no problem with it. Comfort is the most important thing, and it’s highly individual. I prefer a roomy fit with little support, but others are opposite. It’s just a matter of figuring out what works best for you.

  20. I ordered the Merrill 2 mm insoles, and they definitely are not flat. The front is 2 mm, but the heel is raised and cushioned, I would guess it’s at least 4-5 mm. I wanted something to take up a bit more space in my Skechers, as the stock insoles are too thick with a 4 mm elevated heel, but disappointed in the Merrills.

  21. Jim O'Donnell says:

    Hi, I was using the 3mm Invov8 However recently they seem to have stopped making them. Which would be the closest thin featureless sinsole to the inov8 3mm? Thank you

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