Hydraulic Hex PlugHydraulic hex plugs are a type of threaded plug used to close off or seal off an open hydraulic line, cylinder, or other component. They typically have a hex-shaped head and are designed to be tightened or loosened with a wrench. Hydraulic hex plugs are often made of MS, steel, or other durable materials and are designed to withstand the high pressures and temperatures found in hydraulic systems.