Properties: The Birkenstock Boston is a true classic that can be worn all year round. Thanks to its sophisticated design and individual adjustment options, the Boston model has long enjoyed legendary status. Modeled on a cork sandal, this model is made of particularly light and very flexible EVA plastic. High-quality EVA plastic is odorless and tested for possible contaminants and combines many properties: it is very light, flexible, shock-absorbing, water-resistant, and skin-friendly. Anatomically shaped Birkenstock footbed made of EVA foam. Upper material, insole, sole: EVA foam from a single cast. Details: water-resistant, washable, very light. Material: EVA. EVA (ethylene vinyl acetate) is a high-quality, very lightweight, flexible material that provides excellent shock absorption. This smooths out minor surface irregularities and provides a gentle cushioning effect with every step.