The protective tube is a silicon carbide recrystallized product, which is produced at a high temperature of 2200 degrees, can withstand a high temperature of more than 1800 degrees, and is invariant. The silicon carbide content reaches 99.9%. High strength, acid resistance, alkali resistance, wear resistance, corrosion resistance and other characteristics, can be used in copper water, aluminum water, and other alloy solutions, is the best protection guard for thermocouples, can also be used for the protection of silicon carbon rods!