Head Fluida Fins with Mesh BagnNew Closed Heel FinnLight Optimized Pivoting Blade (OPB) SystemnOPB: Blade Maintains Optimal Angle throughout the Kicking CyclenOPB: Produces Constant Thrust, Minimizes Fatigue and Produces Fluid Movement through the WaternThe Head Fluida is a New Closed Heel Fin featuring a Light Optimized Pivoting Blade (OPB) System for Easy Kick and a Soft Foot Pocket for Comfort during Extended Use. The OPB Allows the Blade to maintain an Optimal Angle throughout the Kicking Cycle, whereas Traditional Fins achieve this only during a small portion of the Cycle. OPB produces a Constant Thrust, which Minimizes Fatigue and produces Fluid Movement through the water. It is an exclusivity of Mares Head Fins. The Vented Fin Blade is a Composite Material that Flexes to Channel the Water down the Blade for a more Focused Propulsion when Fining. The Foot Pocket is an Open-Toe Design for added Comfort and Fit. Fins are available from Kid's to Adult sizes of Kid's US 9-11.5, 12.5-1, 1.5-2.5, 3.5-4.5 (EUR 27, 31, 34, 36 and Adult sizes US 5-6, 6.5-7.5, 8-9 and 9.5-10.5 (EUR 38, 40, 42 and 44). Fins come in Blue or Yellow colors, includes a Mesh Drawstring Closure Bag, which allows you to Rinse your Snorkeling Set Right-in-the-Bag and Hang to Drip Dry. The Mesh Bag can also double as a Collection Bag while you Snorkel the Reef. Fins are covered by a 24 month limited warranty.