The Combat Essentiality Code (CEC) is a one-character numeric code that indicates whether or not an end item is essential to the operational readiness of a weapon system or the conduct of a military mission; or that an end item is a functional part contributing to the tactical and essential operations of an end item component or assembly whose failure would render the end item inoperable or incapable of fulfilling its mission; or that a repair or secondary depot reparable component is required for the safety and health of personnel, or is required by state or local laws.
A comparison of the code for a National Stock Number (NSN) is made for each higher order equipment application within the Marine Corps supply system. The code actually recorded is the most critical numeric derived from the comparison.