The 081-0131-203 is a red convex non-diffused lens cap indicator base assembly from Dialight's 373 Series, designed for mounting in an 11/16" clearance hole (.688") with a T-3 1/4 miniature bayonet bulb base. The base features brass solder terminals with hot tinned elongated slots, a brass housing with black nickel finish, and includes a brass mounting nut and phosphor bronze internal-tooth lockwasher with white nickel finish. It meets MIL-L-3661C military requirements and provides a watertight screw-in lens cap with mechanical dimming capability for adjustable light intensity. The assembly is commonly used in ground vehicles, aircraft cockpits, naval vessels, power distribution centers, and surveillance systems where reliable visual indication and environmental protection are essential.