Model B570 fire extinguisher contains a special blended Sodium Chloride based dry powder extinguishing agent. Heat from the fire causes it to cake and form a crust excluding air and dissipating heat from burning metal. Metal fires involving magnesium, sodium, potassium and sodium-potassium alloys can be successfully extinguished with this extinguisher. There is data showing that zirconium, uranium, titanium, and powdered aluminum fires can be controlled and extinguished with this unique extinguisher. 53lb. shipping weigh