Prime Scuba Military Rubber Fin Excellent Propulsion and Comfort in Vented Fin, Durable Rubber Construction Provides Exceptional Speed with Minimal Effort Water Flows-Thru Vents on Weaker Down-Stroke of Fining, Vents Reduce Pressure, Providing Less Strain on Leg Up-Stroke Provides Maximum Power and Propulsion, Adjustable Heel Strap Secures Strap for Ease of Pre-Dive Preparation Metal Buckles for Bulletproof Reliability