Use scraps of 4ply, sock or fingering weight yarn to make this hair scrunchie. I’ve also used lace weight mohair.

You’ll need around 15 g/60 metres / 66 yds of yarn for one scrunchie.
You’ll also need an elastic hair tie.

A heavier yarn isn’t recommended for the specific patterns but you could play around with a smaller stitch count to achieve similar in a heavier yarn.

The blog post has the written patterns for both US & UK terms.

Basic crochet stitches are used.