This bonnet pattern is meant to be versatile. The crocheter can use the yarn and hook desired to make the flat crown circle necessary for the size they choose.

You will need:

Choose the hook size appropriate for your yarn. I typically use a size I for a single strand of worsted weight yarn or a size K for either double stranded worsted weight yarn or bulky weight yarn.
Worsted weight yarn (single or double strand)
Or
Bulky weight yarn
Measuring tape or other measuring device
Any accessories you choose to add

Sizes:

Newborn to child age 10