Elastic Gore-Tex tongue construction. Double Layer Engineered Mesh Vibram outsole Always one step ahead: Thanks to the single tongue, you slip into this shoe like a sock – and that's how it feels. At the latest, when you have tightened the BOA Fit System, your foot won't want to go away. With this, the spring steel sole does exactly what the name suggests: on the one hand, it bounces, on the other hand, it gives your gait reliable stability, thus supporting the natural movement with each of your steps. The more efficient use of energy has longer reserves in the mountains. And thanks to the Vibram sole, you have the best chance that the Ducan BOA Low GTX stays where you put it. Let's go.