Vibram FiveFingers KSO - Women's Review
Cons: Difficult to fit comfortably, uneven sole underfoot, some friction and pressure points
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Our Analysis and Test Results
We were excited to get our hands, er, our feet, on the KSO, a legendary model from Vibram's iconic FiveFingers line of minimalist footwear. Ultimately, however, we were disappointed by the awkward fit and feel and the limited versatility.
The Vibram FiveFingers shoes are the poster child of the barefoot and minimalist footwear trend. Vibram says that the KSO has been one of their most successful models to date, so we needed to try it out. Overall, we were disappointed. The sole has layered pieces of rubber which make the ground feel variable and odd, even though these are otherwise very thin at just 3. mm of sole between your foot and the ground.
The sole is also more shaped, in order to provide more rubberized protection around the sides of your foot, and this ended up feeling clunky. This design makes the upper materials less supple and more difficult to fit precisely to your foot — and an excellent fit is a crucial attribute for anything with 5 separated toes. The heel material rises high and is rigid enough that it dug in a little to our Achilles' tendons, which became aggravating on runs longer than 30 minutes, thus limiting these shoes to only short runs or walks. Additionally, the upper materials do not breathe as well as we would have liked for running and feel more like a swimsuit material — so again, great for a warm day on the water, but not for a warm-weather run. Overall, these are a fine water shoe for a float down the river, but not something we would enjoy for long walks or for running.
With the classic separated toe design and ultra-thin 3.5mm sole, these shoes certainly check a lot of the barefoot accuracy boxes that we assembled from our research into this category of footwear. However, when we walk barefoot, we don't feel that the pads of our feet are uneven (which was the sensation with the layered sole design of the KSO), and we certainly don't have an awkward pressure point on our Achilles' tendon.So, how did these do on our barefoot checklist?
- Zero drop from heel-to-toe? Yes, technically, but the sole feels uneven.
- Sole made of one material? One material but multiple, uneven layers.
- Soft and flexible sole? Definitely.
- Thin sole, less than 10mm thick? Yep, just 3.5mm.
- Non-restricting but secure lacing? Velcro and stretchy uppers! But they're clammy…
- No arch support? Affirmative.
- Breathable uppers? Supposed to be, but they felt clammy on warm-weather runs.
- Straight axis, no in-flared shape or curve? Check.
- No forefoot concavity? Check.
- Wide toe box? Well, there are 5 separated toes, so, yes?
The argument for a wide toe box versus 5 separated toes is an interesting one. In our testing, we have tended to prefer a securely fitting shoe with a wide toe box and thin sole, which allows the foot to feel free. The 5 separated toes can feel really fun, but it requires an absolutely perfect, glove-like fit, and this can be hard to achieve since all of our feet are just so different, down to the length of each and every toe. The KSO highlights this issue with the stiffer perimeter of rubber (designed to protect your feet better), which does not allow for as much flexibility of fit.
Consider, also, that when each of your toes are separated, in order to spread them out, you're going to have to stretch the fabric and bend the sole of the shoes sideways. With your toes in a wide toe box, they are less restricted in their ability to splay. In summary, the KSO certainly looks like a foot, but it is more restrictive than some more ordinary-looking minimalist footwear.
At 11.5 ounces for a European size 41, the KSO are on the lighter side of shoes we reviewed, as they should be given the very minimal design. These are just 3.5mm of Vibram rubber and a lightweight, stretchy upper "sock" with a velcro strap to secure the fit. We love the lightness of these shoes as it helps us feel as if we're not wearing any shoes at all.
The Vibram XS Trek sole rubber looks smooth until you bend it and see the way it splits apart in a micro-wave-like pattern. These shoes do not have a lug pattern at all, and thus are less optimized for trail use. The sole design does notably better on smooth river rocks and wet surfaces, however, which matches the design intentions of this shoe.
This is a fun water shoe but does not excel in other types of terrain. The uppers feel like swimsuit material, with a stretchy sock-like fit, and the soles perform above average on wet and slippery surfaces. The fit difficulties and uneven underfoot feel limit the shoes' utility in other areas such as hiking and running.
The KSO is made of simple, durable materials. The sole curves up and around the toes and up the sides of the foot, which improves long-term durability as well as toughness in rough and abrasive terrain. The stretchy uppers are smooth and adaptable, unlikely to snag, and showing little signs of stress at the seams. And the Velcro strap and heel-pull are made of strong strips of thick fabric, securely sewn in place.
The KSO is reasonably affordable compared to other similar footwear. This is a good move on Vibram's part because they are also less versatile. We appreciate these shoes as a decent water shoe for floating the river or kayaking along the coastline.
The Vibram FiveFingers KSO are not a favorite among our reviewers. We can certainly enjoy the fun (if funny) design of Vibram's now-legendary separated-toe design, but not at the expense of the things we love about minimalist footwear. The layered sole design of the KSO make the ground feel sensation underfoot feel uneven and a little odd. And the fit is notably hard to perfect, creating friction and pressure points. Overall, these are a fun water shoe but not versatile enough to be a go-to for long walks, hikes, or for running.
— Lyra Pierotti