Steel compression tube fittings are hard and resilient with a wide temperature range and good corrosion resistance in high-humidity environments. These metal fittings tighten with basic tools and can be used with multiple tubing materials. Buriable gas fittings connect natural and LP gas lines in underground installations and above-ground pipes. Hydraulic fittings are used with hydraulic fluids in hydraulic applications. Instrumentation fittings are made to tighter tolerances for high-precision applications.