Vibram Five Fingers KSO

The Vibram Five Fingers KSO has no arch support and a minimal amount of cushioning or padding --- it is slightly thicker than the Classic and Sprint which have zero insole (the KSO has a 2mm EVA insole). Many, many minimalist runners "cut their teeth" with the KSO --- running 5KS, half-marathons, full marathons, and even ultramarathons in the Vibram five figers kso.