Made of type 321, soft annealed, stainless steel. Helps protect from scale and oxide buildup during heat treating in atmospheric furnaces. Eliminates decarburization buildup. Resistant to chromium carbide precipitation during exposure to high temperatures. Can be used in furnaces up to 2000 deg F. Tool Wrap protects the surface of air hardening tool steels. This pre-cut foil creates an airtight envelope around your part. It can be folded and crease-sealed with ease. Will not tear easily in normal use. Realize the benefits of a vacuum furnace at a fraction of the cost.