Cover dimensions, materials, construction and marking of wire, step/hole and plaque/hole type IQI used for assessing the sensitivity of the radiographic process in revealing the presence of discontinuities. Standard models of each type are illustrated. Recommendations are given for the selection and location of IQI, the viewing of radiographs, and assessment of the IQI percent sensitivity. A graph showing relative sensitivity values for different types of IQI is given in an appendix.