Made a little video of how to work the brim of this hat here.

Size
Circumference at brim: 19 ½” / 49.5cm
Length from brim to crown as worn: 9 ½” / 24cm

Needles
US 4 / 3.5mm circular needle, 40cm / 16” length (for body of hat)
US 4 / 3.5mm DPNs or long circular needle (if working magic loop for crown of hat)
US 3 / 3.25mm circular needle, 40cm / 16” length (for corrugated ribbing on brim)
US 2 / 3mm circular needle, 40cm / 16” length (for brim)
Always use a needle size that will result in the correct gauge after blocking.

Yarn
Fingering weight yarn in the following amounts:
155 yards MC for hat body
40 yards MC for pom pom
(195 yards total for MC)
30 yards CC1
30 yards CC2
25 yards CC3

shown in:
Jamieson’s Shetland Spindrift (100% Pure Shetland Wool; 105m / 115yds per 25g ball)
MC: Oxford; 2 x 25g balls
CC1: Mooskit; 1 x 25g ball
CC2: Cocoa; 1 x 25g ball
CC3: Auld Gold; 1 x 25g ball

Notions
1 stitch marker, tapestry needle for weaving in ends

Gauge
27 sts & 32 rounds = 10cm / 4” over Fair Isle Pattern on 3.5mm needles after blocking
28 sts & 40 rounds = 10cm / 4” in Rib Pattern on 3mm needles after blocking

Construction
This hat is worked bottom up in the round. After working the ribbing the hat is turned inside out to accommodate the folded brim and so that the right side of the corrugated ribbing is showing.