The sole is very light and elastic and has good shock absorbing qualities. 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. Offers the ultimate cushioning 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 sole is very light and elastic and has good shock absorbing qualities.