This hat is mostly made in half double crochet, but uses single crochet rib for the shaping at the top. Included in the pattern are instructions for foundation single crochet and foundation half double crochet, which prevents the starting edge from being tight. There are numbers for three sizes (infant, child, and adult) and two gauges (DK and worsted yarn). What is not included is specific yardage or hook size information. Those are dependent on your gauge, what yarn you use, and how big you choose to make the hat.