Maraflex thread from Guterman, Col 232 Dark Royal Blue  has Micro core Technology.
Maraflex is the elastic sewing thread for household sewing machines. Maraflex is made with the unique Micro Core Technology® (MCT). It creates elastic seams using straight stitch easily – without an overlock or coverlock sewing machine.
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deal for sewing round necklines, tight seams, cuffs on legs and sleeves.  Sew closing and backstitch seams.
 
Use with straight stitch only, with a stitch length of 4 stitches per cm (approx 2.5mm stitch length).
Sew with thread in needle and bobbin. May need to loosen the tension, (fabric depending)
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Needle type - Jersey / Stretch or Super Stretch - size 70 - 80.
 Made from 100% Polybutylene Terephthalate for a high stretch..