Size S/M corresponds to a shoe size of 5-8.5. 

Deep See's Fin Technology gives speed with less effort. This unique open heel snorkeling fin with adjustable strap, neoprene heel pad, and comfortable foot pocket, allows use with or without a boot. The non-vented blade provides efficient water flow to increase power and speed, with less effort. Fin has a molded flex zones that cups and channel water focusing the kick power for maximum thrust. Fin is a composite design using plastic and rubber.