Aqua Sphere Zip VX Fitness Swim Fins Easy-to-adjust buckles for a custom fit Leverages natural kicking motion to produce a springboard effect that boosts efficiency Hole in the blade creates vortices that can be used for increased thrust Narrow blade improves kicking mechanics and reduces fatigue Non-slip pads on fin rails provide traction for a better push off wall Easy-to-adjust buckles for a custom fit