Promate Cyclone Scuba Dive Rubber Fins - FN590*From the demands of the divers with military specifications, we are proud to recommend to you our solid black open heel rubber fin. This fin is made of antioxidant compound rubber that enhances the performance while keeping the blade consistently in appropriate hardness. The draining holes reduce resistance when you kick the water in making a forward propulsion. They are also helpful in gathering full kicking strength by moving the power to the front