The raised toe bar encourages the natural gripping motion of your feet, thus exercising your legs. The 2 straps can be individually adjusted to your foot width using the metal pin buckles. The Birkenstock Unisex Arizona Birko-Flor Sandals come with two straps that stand for timeless design and comfort factor. The Birkenstock Unisex Arizona Birko-Flor Sandals feature Birko-Flor upper that is made of easy-to-care-for and hygienic PVC, which has been lined on the inside with a soft, breathable layer of fleece. This high-quality material is very gentle on the skin and it’s comfortable while also being very durable. The flexible leather lining, which is gentle on the skin, nestles up softly against your foot and adjusts to its contour. The open-pored and thus very breathable surface makes for a comfortable foot climate, even during more strenuous physical activity. EVA (Ethylene Vinyl Acetate) is a high-quality, very light, elastic material with extremely good cushioning. It smoothes out slight irregularities in the floor and ensures that every step is softly cushioned. The raised toe bar encourages the natural gripping motion of your feet, thus exercising your legs. The 2 straps can be individually adjusted to your foot width using the metal pin buckles.