You can use suggested yarn and needles, or any other option that gives you the same gauge.

Yarn : 1 colour, Gjestal Ulla
4 balls of 50 gr = 200 gr. 50 gr = 95 meter

Gauge : 18 knit stitches on needle US 8 / #5 = 10 cm.
The neckwarmer is knitted with needle US 10 / #6

Knitted back/forth and in circular with a fun relieff pattern