Sporasub Lady Spitfire Black Full Foot Freediving Scuba Diving Fins For Women It features a thermo rubber foot pocket available in size 37/39 The black material, harder, is used for the parts that need to transmit the power from the leg to the blade Spitfire Lady is the first freediving fin designed specifically for women The blue material, softer, is used for the areas in contact with the foot which have to be more comfortable