BJ Enterprises Black Knight Liquid Level Tank Gauge displays numbers that decrease as the fluid level lowers, indicating how many inches are left until the tank is empty. This unit comes with a nickel-plated brass chain that measures from 99" to 0" with a large, mechanical number display. The gauge also features a molded housing, a direct drive, 2" NPT threads, and oversized VERTICAL floats with a swivel assembly. (The Black Knight is not intended or recommended for use with gasoline or highly flammable liquids.)