The 203-0131-203 is a red convex lens cap with complete blackout mechanical dimming feature designed for the Dialight 373 Series indicator base. This component provides adjustable light intensity control through mechanical dimming, offering full blackout capability when fully closed. The lens cap is constructed with a convex design and features non-diffused optics, meeting MIL-L-3661C requirements for military applications. It is compatible with the T-3 1/4 miniature bayonet bulb base and integrates with the watertight screw-in assembly for use in demanding environments such as aircraft cockpits, naval vessels, ground vehicles, and surveillance systems.