Superior Heat & Fire Resistance: Engineered to withstand extreme temperatures and exposure to flames, ideal for protective clothing of firefighters, emergency responders, and race car drivers. Versatile for Special Sewing: Compatible with sergers and sewing machines, suited for heavy-duty stitching in firefighters' attire, racing suits, automotive components, and aerospace gear, ensuring maximum thread performance. Electrical Insulation Properties: Provides reliable electrical insulation, making it suitable for aerospace and electrical industry applications where safety and durability are critical. Stable Heavy Duty Thread: Crafted from high-strength aramid fibers, this serger thread ensures exceptional durability and long-lasting performance for demanding sewing applications including protective gear and automotive heat-resistant projects. Extra-Long Usage Length: Each spool contains 2000 meters of 40/3 gauge thread, providing extended sewing capability that minimizes spool changes and enhances productivity.