Tan Delta Force Fins: Patented toes free foot pocket that reduces cramping, and upcurved V-shaped blade that channels water for maximum directional control and thrust. Maximize the "tangent delta"—the amount of energy recovered for the energy applied to any material The ultra snappy blades give you maximum propulsion efficiency Beautiful enough to be in the permanent collections of the New York Museum of Modern Art Each pair is personally signed by fin designer Bob Evans