Gauge port adapters are specialized fittings that provide a connection point for pressure gauges in hydraulic and pneumatic systems. They allow the user to install a pressure gauge, diagnostic nipple, or sensor inline in a hydraulic system. They are made from zinc/nickel-plated carbon steel which offers reliability and long life of use, and have a hexagonal shape for easy installation and removal with a wrench.

They are offered in JIC, ORFS, ORB, BSPP, JIS, Komatsu, and DKO (24°) specific configurations.

And one common type of gauge port adapter which NJ offered is the "tee" fitting, has a single port for the gauge (can be SAE/NPTF thread) and two additional ports for connecting to the hydraulic system, such as 6564, 6574, FS6564, FS6574.