| C | The item has critical features such as tolerance, fit restrictions or application. Nuclear hardness properties have not been determined (not valid for input). |
| E | The item is an Aviation Critical Safety Item/Flight Safety Critical Aircraft Part (ACSI/FSCAP) and is specially designed to be or selected as being nuclear hard. |
| F | The item is an Aviation Critical Safety Item/Flight Safety Critical Aircraft Part ((ACSI/FSCAP). |
| H | The item is specifically designed to be or selected as being nuclear hard (i.e., it will continue to perform its designed function in an environment created by a nuclear explosion). The item does not have other critical features. |
| M | The item is specifically designed to be or selected as being nuclear hard. In addition the item has other critical features such as tolerance, fit restrictions or application. |
| N | The item does not have a critical feature such as tolerance, fit restrictions or application. Nuclear hardness properties have not been determined (not valid for input). |
| S | The item is a non-aviation Critical Safety Item (CSI) whose failure will result in serious damage to equipment or serious injury or death to personnel. |
| X | The item does not have a nuclear hardened feature or any other critical feature such as tolerance, fit restriction or application. |
| Y | The item does not have a nuclear hardened feature but does have other critical feature(s) such as tolerance, fit restriction or application. |