The Jackson Baby Hat by Allison calls for 1 skein of worsted weight yarn (pictured in Tosh Vintage).
Other beautiful worsted weight options include:
220 Superwash Merino
Click here for even more worsted weight options.
There are 5 sizes available (S 16" circumference as shown to XXL 24" circumference).
It's knit using size US 7 needles.