This is the IST F1 Traditional Rubber Scuba Diving Military Dive Fins Open Vent Fin Features: Traditional rubber fin with proven design By combining features such as special blade curvature, varying degree of flexibility and structural ribs, the product is positive forward thrust with spring-like effect The open vents efficiently channels the water flow to give added energy saving effect Stainless steel spring fin strap compatible (item no.: FS11) The snapback quality and many years of reliability, makes this fin an unbeatable value!