This is the Mares Full Foot Volo Race Scuba Diving Fins with OPB System Features: OPB (Optimized Pivoting Blade) Fin Technology that ensures the blade at the optimal angle at all times providing increased efficiency and power Channel Thrust Technology system for optimal water channeling Maintaining optimal thrust throughout every phase of the fining stroke minimizes fatigue Soft anatomical foot pocket, with ribbed insole for an improved fit and a dramatically more efficient fin stroke The combination of OPB and Channel Thrust technology make the Volo Race the perfect fin for divers who want to increase their efficiency with minimum effort. OPB for controlling and optimizing the thrust angle. Channel Thrust technology for perfect routing of the water flow. Rubber covered stabilizers provide improved performance. Divers and snorkelers alike will enjoy this easy kicking fin.