These are the OMS Monoprene Slipstream Scuba Diving High Performance Fins These awesome fins feature: Comfortable foot pocket A lightweight, neutrally buoyant Monoprene resin A proven fin design that results in better trim positioning with maximum thrust on the down kick and minimal resistance on the up kick Comfort fit adjustable straps A fin so revolutionary that the U.S. Navy cut their swim time by 1 minute on a 500 Meter Swim !