FinKid Our Mermaid FinKid and FinTeen were designed for everyday as well as occasional usage. The monofin is made from the finest neoprene and polycarbonate. It is light and ergonomic which helps children swimming with little effort. The Mermaid Monofin FinKid and FeenTeen is recommended for women and children of all ages and is suitable for most shoe sizes. FinKid fit Mermad Tail’s sizes from size 3Y to 9Y. Please make sure you will purchase proper size of fin with your tail.