Materials
Yarn: about 180-210 yd (165-210 m) of worsted weight yarn. I used Malabrigo Rios. This is a lighter worsted weight yarn (210 yd/200 m per 100 g). If your yarn is heavier, you might run out of yarn or have a larger hat. If you are worried about running short of yarn, you can opt for a single brim.

Needles:
Size US 6 (4 mm) needles, or whatever size is needed to make gauge, 16-inch (40 cm) circulars, and double-pointed needles (or your preferred method of medium- and small- circumference knitting in the round).
Size US 4 (3.5 mm) needles, or 1-2 sizes smaller than your main needles, 16-inch circulars for knitting the brim ribbing.

Gauge:
20 stitches and 27 rows in 4 in x 4 in (10 cm x 10 cm) of stockinette, using the larger needles.

Sizing:
This hat is snug on my 22-inch (56 cm) head. Due to the stretch of the cables, I think it would fit about 18-22 inches (46-56 cm). You could try a larger needle for a larger hat. To adjust the length, you can easily add or subtract a full repeat (16 rnds), or a half repeat (8 rnds). My finished hat is about 10.5 in (26.5 cm) deep, unfolded and 6 in (15 cm) across laid flat.