These are attractive shoes. They are made of EVA, the same material used in Crocs and some Birkies. It's petrochemical but without the nasty chemical smell that some shoes have. It's certified vegan: no animals were harmed, except maybe a few dinosaurs. They're definitely small: I usually wear a size 8 and they're described as M8W10, but they're smaller than I'm used to. Untying and retying the loop helps, but it would still be nice to get a larger size.