Hydraulic fittings come in multiple thread, material, and shape configurations and are often used to connect hydraulic ports, hydraulic hoses, and hydraulic tubing to pumps, motors, etc.
Hydraulic fittings are also called steel adapters. The most common thread styles include NPT (national pipe thread), JIC 37 degree cone, O-ring boss, O-ring face seal, British thread (can be BSPP or BSPT thread), and metric thread. Less commonly, they can come in Code 61, Code 62, CAT style flange and compression tube.
Hydraulic fittings are mostly commonly made with carbon steel.