FinTeen 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. FinTeen fit Mermad Tail’s sizes from size 11Y – up Please make sure to order the right fin size with your tail.