Gauge: 19 sts in 4inches (10cm) in stockinette stitch

You will need: Worsted yarn (up to 80 grams for adult size), knitting needles to obtain the gauge (please make sure you make a gauge swatch!) for knitting in the round, darning needle to weave in the yarn ends.
Please make a gauge swatch to make sure you match the gauge! The needle size will vary from yarn to yarn and from knitter to knitter! Please check your yarn label to see the needle size the yarn manufacturer recommends to obtain the gauge, make a gauge swatch and adjust the needle size if needed.

Regarding the sizing: the scarf is stretchy. It will fit most of those who are in their according age/size. 5+ size will stretch to fit most adult heads (up to 60cm / 23.5in circumference).