499712-1 is a keying plug designed for use with size 20 socket contacts in HD, HDE, and HDP subminiature D connector receptacles. This component is manufactured from polyphenylene oxide material and features dimensions of 0.200 ± 0.010 inches [5.08 ± 0.25 mm] in length with a maximum diameter of 0.115 inches [2.92 mm]. The keying plug is installed taper-end first into the front of the receptacle and is compatible with AMP-LATCH electrical connectors for HD22 socket contacts. This accessory is commonly used to provide selective positioning and keying functions in subminiature D connector assemblies, ensuring proper mating alignment and preventing incorrect connections.