Extrema Ratio’s Ultramarine was designed with the Naval Experimental Diving Unit of the United States. This knife was made to be a versatile tool, especially for underwater operations, so there is no dangerous piercing tip to cause mishaps. It’s an underwater, survival, and combat knife with a black burnished, partially serrated blade that’s made of exceptional Bohler N690 stainless steel and the inside-hilt blade tang underwent a special process to prevent corrosion. This fixed blade knife set includes a carrying case, maintenance spray-can, a Cordura fabric ankle sheath, and two belt clips that makes separate use of the inner hard sheath possible. Key features of Extrema Ratio Ultramarine N.E.D.U. Black (5.5″): * 10.88″ (27.64cm) overall. * 5.5″ (13.97cm) black MIL-C-13924 burnished partially serrated Bohler N690 stainless blunt tip blade. * Black nylon handle. * Sheath comes without an upper flap. * The inside-hilt blade tang undergoes a special cataphoresis process to prevent corrosion. * The knife is supplied in a case with: a Cordura fabric ankle sheath, two belt clips allowing for separate use of the inner hard sheath, and a blade maintenance spray-can. * Hardside carrying case.