This coding system is intended to provide a convenient means of identifying the various tube, pipe, hydraulic hose type and hose fittings, not intended for use in aircraft and of transmitting technical or engineering information relating to them wherever drawings or other pictorial media may not be readily available. The code has been kept flexible to permit expansion to cover new fitting categories or styles and, if the need develops, the inclusion of additional materials. The system is also compatible with automatic data processing equipment. It is not intended that this code should supersede established systems or means of identification. Therefore, it should be the prerogative of the user to apply the code which best satisfies his requirements.