Black EVA plastic type Birkenstocks. Sturdy and lightweight and waterproof great for summer or travel. Size 42 but I’m including the measurements from front to back because they seem to run a bit larger than standard leather and cork Birkenstocks. I wear a 41 or 42 in Birkenstocks leather sandals and shoes but these seem roomier more like 43 or 44, which I’ve heard is typical for the EVA version of Birks. Anyway these are great quality shoes that will last a long time for your summer adventures!