This pattern is called Snowflake Cowl and uses an Aran weight yarn. Although gauge is not critical you should aim for similar to that written,

I have used both Aran weight yarn to make the cowl and also used an alpaca dk doubled both using 5.5mm needles. the dk doubled used a little more yarn up to 130grams but was thicker and more snuggly so there is more than one choice of yarn to use which will give similar results and size. Just play with the pattern and see what you prefer.

Knitted in the round and with a pretty snowflake pattern it looks better in a plain colour than a variegated as with a the variegated you tend to lose the effect of the pattern.

I hope you enjoy knitting your cowl either for yourself or for someone as a present, use the nicest yarn you have and enjoy!