The purpose of this report is to provide recommendations for marking wire and cable insulations to meet legibility requirements. This information is generic and applies to any type of wire marking system, such as an ultraviolet (UV) laser marking system or an inkjet or other ink based wire marking system. This report is limited to the legibility of humanreadable characters and does not address bar code or other machine-readable symbols. In this report, the term wire refers to jacketed cables and fiber optic cables in addition to individual wires. This report defines the factors that affect the legibility of markings on wiring. Two generic types of variables affect legibility: stimulus variables and environmental variables. Stimulus variables are those factors involving the mark itself. This ARP establishes a set of guidelines for key stimulus variables that contribute to legibility and which should be taken into consideration in the course of specifying and using wire marking equipment.