Four Seasons Stitching. The Simple Answer to your manufacturing need for Fire Retardant Tape Edge Sewing Threads. The company's new line of Fire Retardant Tape Edge Sewing Thread, T60 Safe-Tik FR Thread, can help your comapny to decrease waste, reduce production line downtime, and cut overall FR Thread cost. The unique construction of the T60 Safe-Tik FR Sewing Thread can, even, reduce the amount of time and money spent on replacing needles in your commercial tape edge sewing machines.