Mettler - Seraflex Elastic Sewing Thread - Old Tin
Seraflex is the perfect sewing thread for highly elastic seams on all elastic fabrics.
Due to its innovative raw material PTT (37% renewable raw material) an elongation of approx. 65% is achieved, making all seams highly elastic.
Seraflex makes a straight stitch extremely stretchable, therefore eliminating the need to use a stretch stitch, or twin-needle stitch on knit fabrics. Plus it greatly reduces the risk of threads breaking when seams are stretched.
So just use it as your top and bottom threads, and set thread tension to the lowest setting.