This cowl is knitted in the round, using 6mm needles and 200m of worsted-weight (10 ply) yarn. I used 2 balls of Zealana's gorgeous Heron (Lichen colourway) for my cowl, and I'd say it is best suited to a light, airy yarn such as this. If you can't get Zealana, and are looking for an alternative, I think it would also look lovely in a worsted-weight possum, angora or mohair mix yarn.
Knitted up, the cowl measures 13" (33cm) across and 12" (30cm) tall and is a nice size for a medium - large-sized head. Cast on a smaller number of stitches for a small-sized head (suggest 84) or knit another repeat of the single eyelet pattern for a longer neck/more fabric.
An alternative look for this cowl would be to do knit it at double its width (cast on 180 - 200 stitches instead of 90) and knit only half the width. It would then be long enough to twist in half and wear as a very cuddly, deliciously soft cloud of warmth around your neck. I estimate you'll need around 400m of worsted-weight y