About this item Seamless Compatibility: Crimp hose fittings are designed for easy connection with 3/8″ I.D. hydraulic hoses. These fittings have a 3/8″ NPTF external thread end, ideal for fluid power systems and hydraulic applications. Versatile Application: Hydraulic fittings are made of premium carbon steel, can endure temperatures from -65°F to 500°F, suitable for use with industrial fluids, including petroleum-based fluids, gasoline, fuel, and lubricating oils. .