UK sizing. The Meindl Vakuum boots are comfortable right out of the box! This stout and comfortable trekking boot will get you through even the harshest, most demanding terrain. - Memory Foam System Vakuum structure: the shoes have memory foam (shown in yellow in the additional image) which offers a snug fit without causing pressure - Form-fitting Air Active Vakuum footbed - Nubuck outer - Gore-Tex laminate - Protective scree collar - Digafix lacing - Class B rated: good ankle support and a relatively stiff midsole structure