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Vibram FiveFingers KSO Review

For those who fully embrace the barefoot lifestyle, this shoe performs well on the road and in the gym
Vibram FiveFingers KSO
Photo: Vibram
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Price:  $85 List | $84.95 at Amazon
Compare prices at 2 resellers
Pros:  Flexible, breathable, surprisingly durable
Cons:  Very particular sizing, lengthy break-in time, goofy
Manufacturer:   Vibram
By Aaron Rice ⋅ Review Editor  ⋅  Dec 1, 2020
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66
OVERALL
SCORE


RANKED
#7 of 9
  • Performance - 30% 6
  • Barefoot Accuracy - 25% 8
  • Weight - 15% 8
  • Traction - 15% 5
  • Versatility - 10% 5
  • Durability - 5% 7

Our Verdict

Vibram is as synonymous for durable outsoles as Kleenex is for tissues. The company was the first to introduce barefoot shoes to the market with their FiveFingers design. Often it is easy to distinguish those who fully embrace the barefoot lifestyle by their indistinguishable choice in footwear, and for those who love them, the FiveFingers KSO is an improved version of Vibram's original shoe. For seasoned barefoot runners and minimalist enthusiasts, this surprisingly durable cross-trainer will comfortably carry you over roads and into the gym. Even though the soles are tacky, they are not exactly trail worthy, nor would we hail them as the most versatile shoe we tested. But if the criteria of barefoot accuracy, flexibility, and breathability are top on your list, the glove-like fit of the KSO is tough to beat.

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Pros Flexible, breathable, surprisingly durableSuper lightweight, exceptional ground-feel, freedom of movementSuper tacky outsole, low profile, extra durableTough exterior, stable, snug lacing systemDurable, versatile, minimal stack height
Cons Very particular sizing, lengthy break-in time, goofyInconsistent grip, short stock laces, potentially short lifetimeOversized, not very versatile, outsole loses grip when dirtyOdd flex pattern, decreased sensitivity, lack of dexterity in toesWeighty, bulky, overly padded upper
Bottom Line The original, and still one of the best shoes when it comes to pure ground-feelA perfect mix of road and trail runner, our Editors' Choice for outstanding barefoot accuracyA true barefoot gym shoe designed with durability in mindA FiveFinger shoe that earns our Top Pick for Adventure and Trail RunningMuch more impressive than it looks, this versatile trainer stays true to its barefoot design
Rating Categories Vibram FiveFingers KSO Merrell Vapor Glove 4 Inov-8 Bare-XF 210 V2 Vibram V-Trail 2.0 Xero Shoes Prio
Performance (30%)
6
7
9
8
8
Barefoot Accuracy (25%)
8
9
7
6
8
Weight (15%)
8
8
6
7
5
Traction (15%)
5
7
7
8
6
Versatility (10%)
5
7
6
6
7
Durability (5%)
7
6
8
9
8
Specs Vibram FiveFingers... Merrell Vapor... Inov-8 Bare-XF 210... Vibram V-Trail 2.0 Xero Shoes Prio
Style Barefoot road Barefoot road Barefoot gym Barefoot trail Barefoot road
Weight (oz per shoe) 5.5 oz (size EU 42) 5.4 oz (size EU 42) 7.5 oz (size US 9.5) 6.9 oz (size EU 42) 8.4 oz (size US 9.5)
Stack Height (mm) 3.5 mm 6.5 mm 4.5 mm 3.7 mm 5.5 mm
Heel to Toe drop (mm) 0 mm 0 mm 0 mm 0 mm 0 mm
Outsole (mm) 3.5 mm, XS Trek Performance Rubber 3.5 mm, Vibram TC5+ 3 mm STICKY rubber 3.7 mm, Megagrip Rubber 5.5 mm, FeelTrue Rubber
Midsole (mm) None None None 2 mm EVA None
Insole None None 3 mm Power Footbed None Optional 2 mm
Upper Material Stretch polyamide, polyester, Hypalon Cordura mesh and TPU Lightweight mesh 3D Cocoon Mesh Mesh with synthetic leather overlays
Best For (running, hiking, etc.) Gym, running Running, gym Gym, running Running, hiking Running, gym
Width Options Regular Regular Regular Regular Regular

Our Analysis and Test Results

The KSO is the closest thing to the original FiveFingers design, with minimal outsole padding and a zero-drop ratio. "KSO" stands for "Keep Stuff Out," and the hook-and-loop closure fastens tightly around your foot to prevent rocks and sand from getting inside — a huge improvement over the original FiveFingers shoe.

Performance Comparison


Dry pavement is truly this shoe's wheelhouse.
Dry pavement is truly this shoe's wheelhouse.
Photo: Aaron Rice

Performance


The FiveFingers KSO is designed as a versatile outdoor shoe, but we actually find it's more suited to a life in the gym. The tacky, Vibram XS Trek outsole climbs well enough on dry, rocky trails, but when it comes to running or walking over wet surfaces, even wet concrete, the lack of lugs or wells to shed water left us slipping and sliding all over the place. The stretchy, polyester upper is designed much like a water shoe and dries equally quickly. With their low-profile design, these would make great companions for river crossings on backpacking trips. Just make sure you give the soles a quick wipe before trying to scramble up the rocks on the opposite bank.

Lugless soles make this shoe slippery on wet surfaces, but...
Lugless soles make this shoe slippery on wet surfaces, but individually articulated toes allow you to grip well on anything dry.
Photo: Aaron Rice

When it comes to hot, dry climates — either in the gym or running roads — the lightweight uppers are breathable and super comfortable, even in the heat of the summer. For those truly confident gym-dwellers, there are few other shoes in this review that perform as well — just be ready for more than a few funny looks. The KSO nearly perfectly emulates the natural shape of your foot. Combined with its tacky, non-marking sole, it's almost as if you developed naturally sticky, Spider-Man-like feet. However, although this shoe is nimble, the rounded heel-cup doesn't quite provide the same support for heavy lifts as some of the other gym-specific shoes we tested.

Digging in and springing from your toe is a fundamental of running...
Digging in and springing from your toe is a fundamental of running, and was highlighted in the heavy sand of this arroyo outside of Santa Fe, NM.
Photo: Aaron Rice

Barefoot Accuracy


As the original and still one of the best designs on the market, the KSO is essentially a foot-glove and rightfully provides an accurate barefoot experience. A lightweight upper wraps seamlessly into a 3.5mm outsole in a way that feels like you're pulling on a heavy-duty sock. Considering that the ultra-thin microfiber insole is sewn-in directly and that there is no midsole, you can expect to feel every bump in the road. We do appreciate that the outsole is slightly thicker under the ball of the foot, working three-fold: to beef up the natural rocker in the ball of your foot, to act as a bit of a brake running downhill, and to provide just enough extra protection from thorns and sharp rocks.

While we always suggest visiting your local shop to try shoes on in-person to find the right fit, it's even more important to size the KSO properly. In order to minimize the chance of hot spots and blisters, we also highly suggest purchasing a pair of toesocks — our testers are big fans of Injinji socks, even if we're not wearing FiveFingers shoes.

The Injinji toesocks are a necessary purchase if you plan on running...
The Injinji toesocks are a necessary purchase if you plan on running or hiking in these shoes.
Photo: Aaron Rice

The 360-degree, single hook-and-loop velcro closure of the KSO pulls your foot firmly into position, bringing the heel-cup right up against your achilles and your toes right to the front of their individual boxes. The FiveFingers design allows for individual articulation of the toes, which translates to improved grip and a natural boost when running. Although the FiveFingers shape might suggest that these will fit any foot, we've found that these best suit those with narrow to mid-width feet — those with particularly wide feet might find that the closure system to be uncomfortably tight.

The hook-and-loop design pulls a strap around your heel from both...
The hook-and-loop design pulls a strap around your heel from both sides, firmly securing your foot in place and giving these shoes a snug fit.
Photo: Aaron Rice

Weight


As the company that helped define minimalist footwear, the Vibram FiveFingers KSO provides little more than a protective foot wrap. Weighing in at only 5.5 ounces per shoe, these are rightfully one of the lightest shoes we tested.

Simple and lightweight, these minimal shoes are not much more than...
Simple and lightweight, these minimal shoes are not much more than the Vibram sole and polyester/mesh upper.
Photo: Aaron Rice

Combining this with outstanding barefoot-accuracy, and it should come as no surprise that wearing the KSO doesn't feel like much when you have it on. We wouldn't exactly describe the fit as airy, though this simple design is lighter even than most sandals. However, even when soaking wet, this shoe is incredibly lightweight. Heel loops allow you to clip this ultralight pair of shoes onto a waist belt and present an interesting option for close-toed river shoes for warm water anglers.

A majority mesh construction allows these shoes to not only breath...
A majority mesh construction allows these shoes to not only breath well, but also to effectively dump water and quickly dry out when used as a water shoe.
Photo: Aaron Rice

Traction


Despite its foot-mimicking pattern, the XS Trek outsole is not nearly as grippy as it is flexible. The proprietary, non-marking rubber is tacky enough for any gym floor, and the enhanced flexibility helps you naturally grip with your toes on trails or rough terrain. But even if it's just a little damp out, be ready for some proprioception training. With an essentially smooth bottom, the KSO slips and slides over wet surfaces, whether those are rocks or concrete. If you live and exercise in any climate where it regularly rains, we suggest looking at other shoes in this review.

We tried, but the KSO was not comfortable running over wet rocks...
We tried, but the KSO was not comfortable running over wet rocks. Here, one of our reviewers is slowly running to higher, safer, and drier ground.
Photo: Thomas King, Ryan Baham

Versatility


Don't be led off trail by the namesake "Keep Stuff Out" acronym. The KSO is best suited to road running or gym workouts. The lightweight, breathable upper performs great in hot, dry climates and does dry out quickly after running through streams, which makes this a great adventure running shoe option for those diehard barefoot runners. Style comments aside, these are indeed a serious barefoot shoe and should not be considered as an easy way to transition into this running style.

In a style-class all their own.
In a style-class all their own.
Photo: Aaron Rice

Durability


Despite a fairly simple structure, the quality and durability known to Vibram soles extends through the rest of KSO. Areas that often see the most wear-and-tear — around the ends of the toe box(es), the heel, and around the sides — are provided additional support thanks to a wrap-around sole. Additionally, the sole is glued and sealed to both the heavy-duty Hypalon that acts as a quarter stiffener, and the abrasion-resistant polyamide upper. We ran miles of the rough sand arroyos that stripe the Southwest, and these shoes emerged practically spotless.

It's nearly impossible to pull this shoe on without using the heel...
It's nearly impossible to pull this shoe on without using the heel loop, so designers used hearty Hypalon and securely backed up the loop with multiple box stitches.
Photo: Aaron Rice

Value


The KSO is certainly a specialty shoe. But for those who firmly believe that barefoot shoes are the basis for holistic training, this classic will continue to impress. While not as versatile as other trainers we tested when it comes to bridging the gap between road and trail, these true barefoot shoes will surely help you train proprioception and gait.

A versatile training and adventure shoe (think raft trips), there...
A versatile training and adventure shoe (think raft trips), there are a lot of reasons why this design has stood the test of time.
Photo: Aaron Rice

Conclusion


If you are looking for an authentic barefoot experience and have the confidence to stand up to a few sideways glances at the gym, then you likely already know the secret of training in a shoe like the Vibram FiveFingers KSO. While other companies have certainly improved on barefoot shoe design, these classics still stand up to the test of time.

Aaron Rice