The Franca is a stylish and feminine new slip-on sandal featuring criss-cross straps. The original contoured cork footbed conforms to the shape of your foot and features pronounced arch support with a deep heel cup and roomy toe box. Oiled leather can be recognized by its untreated surface. Birkenstock purposely does not treat surface grains and other characteristic features. Birkenstock uses sturdy leather with a thickness of 2.8 to 3.2 millimeters as upper material.