Certech® Exp is Lundhags own shell construction for the lower parts of the boots. A technology built-up in 3-layers. The outer layer is the durable, but light material Liba Smart, the midlayer uses Eva for insulation and shock absorption, and the inner layer is micro fiber, which lines the entire inner for best comfort. Together, the layers in Certech® Exp create a light and durable protection against everything that a pair of boots can be exposed to.