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.

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

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.

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

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!