What is fiberglass? Glass fiber yarn performance features Glass fiber yarn is made of glass ball or waste glass by high temperature melting, drawing, winding and weaving. Fiberglass yarn is mainly used as electrical insulation material, industrial filter material, anti-corrosion, moisture-proof, heat insulation, sound insulation, shock absorption material. It can also be used as reinforcement materials to make reinforced plastics or reinforced gypsum and other FRP products. Using organic material to cover glass fiber can improve its flexibility, used for packaging cloth, window screen, wall cloth, covering cloth, protective clothing and insulation materials.