I have made multiple hats using this pattern and I have used different sized needles and different weights of yarn. The pattern below is what I used for the pictured hat. This was the original hat that I did.
Sz 9 needles
Cast on 38 stitches
Row 1: P9 K1 P28
Row 2: K9 P1 K28
Row 3: P9 K1 P28
Row 4: Cable 3 in front K3, K3 from cable needle, K3 P1 K28
Row 5: P9 K1 P28
Row 6: K9 P1 K28
Row 7: P9 K1 P28
Row 8: K3 transfer 3 to cable needle hold to back K3, K3 from needle P1 K28
Repeat these 8 rows until hat is desired length. Measurement from cast on edge to needles should be about an inch less than the circumference of you head. Cast off leaving an extra long tail for seaming at the end. Seam the two selvage edges together and turn inside out. Fold hat into even fourths as shown in the picture. Seam edges and flip hat right side out again.
Hope these instructions are clear! I have gotten a ton of compliments every time I wear this hat! I have also made some in lighter colors for spring/summer!