18 V Zener — what the ratings mean on the bench
The 1N6006C is an 18 V Zener diode in a DO-35 axial-lead package, rated for 500 mW continuous dissipation. That 18 V nominal at ±2% tolerance means the actual breakdown voltage lands between 17.64 V and 18.36 V — tight enough for a precision shunt reference or a voltage clamp where the 5% standard part would leave too much guard band. The -65°C to 175°C operating range covers military and aerospace temperature profiles — the junction sees the full swing without derating the power below the 500 mW ceiling until you cross 175°C. Reverse leakage is spec'd at 100 nA max at 14 V, which is 4 V below the Zener knee; in a high-impedance bias circuit that leakage won't shift the operating point.
DO-35 package — board-fit for through-hole repair and legacy designs
The DO-35 (DO-204AH) axial-lead package is the standard 2-lead glass body with 0.020-inch diameter leads. It drops into existing through-hole layouts without a board spin — useful when you're replacing a blown Zener on a legacy controller board or stocking a reference for a long-life design that hasn't migrated to SMD. For a repair bench or low-volume production run that's fine; for high-speed pick-and-place you'd want the tape-and-reel variant (check the base number suffix).