Nextel 312 is an Alumina-Borica-Silica fiber that is braided without the aid of organic, glass or metal inserts. This sleeving retains strength and flexibility at continuous exposure to 1200°C (2200°F). Short exposures to 1425°C (2600°F) can be tolerated. Most common metals (except molten copper and tin) do not attack the fibers.

Because Nextel 312 Ceramic Fibers contain no residual acids or chlorides, there are no chemicals present to corrode or etch the wires. Even in a test involving exposure to 96 percent relative humidity, no noticeable electrolytic corrosion was detected. Not recommended for use in abrasive environments without the protection of Inconel¨ overbraiding or a thermowell.

Silica is chemically compatible in many environments such as air, oxygen, nitrogen, argon, ammonia, carbon monoxide, chlorine, hydrogen chloride and sulfur dioxide. It is also stable in a vacuum, in contact with water, various hydrocarbons, ammonium hydroxide, and hydrochloric, nitric, and sulfuric acids.