Unprocessed and semi-processed natural rubber, gutta-percha, gum, asbestos, and mica; plastics and resins in extruded form for use in manufacture; packing and insulating materials; stopping materials in the nature of packing and stuffing materials of rubber and plastic; flexible pipes, tubes and hoses, not of metal; acoustic insulation materials; fire resistant and fire preventive articles and materials for insulation and structural purposes, namely, blocks, boards, plates, sheets, shells, pi...