Sew in seam tape 100% cotton 5mm wide black 10m

This tape is like a shoe lace, it's thin and woven. Made from 100% cotton . Stitch it on seams that's shouldn't stretch like the shoulderseams in a T-shirt. If the shoulder seam has this tape it will not sag.

Not suitable for armholes and necklines, they are not straight and the tape is not suitable for round use. If you want te secure a round seam try formtape by Vilene, that's specially made for it.

(Sometimes dentists will advise it as floss)