From website:

NL31 THREE GAUGE HELMET

Choose between 3 different yarn weights and create a helmet hat in 3 different sizes. Start with the earflaps, join and knit circular for body of the hat, finish with a tassel.

SIZES:
Child 6-8 yrs (Med adult, Lg adult)
Fits head measurement: 20” (22”, 24”)

YARN:
Sport: 100 (100, 150) gms, 170 (180, 230) yds
Worsted weight: 100 (100, 150) gms, 150 (170, 220) yds
Bulky: 100 (100, 150) gms, 110 (120, 135) yds

NEEDLES:
Sport: size 6. Worsted: size 7. Bulky: size 10 1/2