Check the listing for details. BJE Black Knight Tank Level Gauge. Condition: Used. Listed at 156.00 USD. The BJE Black Knight Tank Level Gauge is a high-quality air pressure gauge designed for use in tanks to monitor the level of the fluid inside. This gauge is specifically tailored for industrial applications, providing accurate readings to help with maintenance and troubleshooting. Its sleek design and durable construction make it a reliable tool for measuring air pressure in various systems.