Vulcanized Cellulose Fiber for all electrical insulation. Gray insulating paper. .010" thick. used in switches, under terminals, in transformers, etc .where mechanical strength is required. Its qualities of toughness, flexibility, and edge-tearing resistance combined with high dielectric strength and ready absorption of insulating varnish have led to its predominant use as an improved motor slot call insulation. Dielectric strength 3000 volts. 10" wide roll contains 240 sq. inches.