Vibram FiveFingers KSO Review

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.

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 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, 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.

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 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 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 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. 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.

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 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 are a lot of reasons why this design has stood the test of time.

Photo: Aaron Rice

Conclusion