I live in the dark and cold north, and I knit these hats in Fishermans rib with reflective yarn and an extra strand of mohair. The hat becomes wonderfully warm and soft and can be seen well by the roads in the dark. They can of course be knitted in a different yarn, without the reflective thread with the same gauge.

Yarn:
3 x Svarta fåret reflective yarn 50g = ca 50 m.
1 x Sandnes Tynn silk mohair 25g = ca. 212m.
Circular needle: 5, 5 mm. 40cm. (UK 5, US 9),
6, 0 mm. 40cm. (UK 4, US 10)
You also need: stitch markers, rows counter and a tapestry needle.