Atomic Aquatics Open Heel Split FinsEven Fish Envy SplitFins.Why? SplitFins deliver more propulsion with less air consumption. All it took was watching the tail fins of fish ? except that we couldn't keep up with them because our traditional fins took too much effort. Using hard kicking paddle fins can result in leg strain, fatigue and cramping. Because of the kick resistance of a paddle fin, divers often "felt" like they were moving fast. But underwater speedometers proved that these divers were actually moving relatively slow. SplitFins deliver more propulsion with less drag and kick with less effort. Reducing the stress and strain of the kick results in greater sustained speed, power and comfort. Independent testing has also confirmed that the SplitFin design significantly reduces air consumption.FEATURESLess Drag, More Thrust, Less Strength is UsedLatest Technology in Composite Plastic Polymer MaterialsLight Fin (Great Travel Fin)Increases Thrust and Reduces FatigueEZ-LOK Squeeze-Style" Quick-Release BucklesEZ-LOK: Snap-On-and-Off with Ease, Will-Not Disengage- AccidentallyRubber Straps with Large Pull-Tab for Easy Donning and DoffingFlexibility and Rigidity for Efficient PropulsionLess Air ConsumptionPower Rails: Backbone of the Split Fin, Highly-Resilient, Storing and Releasing Energy with Every KickSemi-Ridged Flex Battens: Control the Precise Wing Shape to Optimize Thrust and Reduce DragLarge Surface Area Blade Improves Pivoting, Turning and Alternate Kick StylesThin, Yet Strong and Highly Flexible Hinge Points Cause Blade to React Quick-and-EfficientlyAnatomically Contoured Foot Pocket Designed to Fit Foot without Stress PointsSemi-Open Toe for Added ComfortInternal Sole Plate, Ridged Platform Beneath-the-Foot, Greater Power Transfer to the BladeSoft, Comfortable Open Heel Foot PocketSplit Fin Men's SizingSmall: USA - 5 1/2, EU - 37-38Medium: USA - 6-6 1/2, EU - 39-41Large: USA - 9-11, EU - 42-43X-Large: USA - 10 1/2-11 1/2, EU - 44-46