The cap is machined from brass with a nickel body finish and comes in a silver color. An integrated chain tethers the cap to the cable or panel so it stays within reach when the jack is in use.
What it fits and where it goes
This cap is intended for use with BNC jacks — the female panel-mount or bulkhead connectors common on RF test equipment, video distribution gear, and instrumentation panels. The nickel-plated brass construction provides adequate RF shielding continuity when the cap is installed, though its primary job is mechanical and environmental protection, not impedance termination.
Construction and tethering
The brass body with nickel finish resists corrosion in lab, broadcast, and light industrial environments. The attached chain is a practical detail for field-service and test-bench use — it keeps the cap from walking off when the BNC jack is mated, which is the single most common way these covers get lost.