100% SERAFLEX® PTT (Polytrimethylenterephthalat) Elastic Stretch Mettler Thread This thread is creatred using a polyester synthesized and patented in 1941 - - -
 
• Perfect for sewing stretchy fabrics
• Thread elongates by aprox. 65%
• Double seam elasticity can be acheived compared to seams with a conventional sewing threads
• Needle size of 70-80 is recommended
• Use both as needle and bobbin thread and loosen tension