This retro-inspired cloche hat has a lacy shells design and slightly wavy edge.
It can be crocheted from any Aran or Worsted weight yarn you wish. In my opinion an Aran or thicker Worsted weight yarn would be best for this hat since it helps the wavy edge, which is slightly flared, hold its shape a bit better.
You'll need about 200 yards of it plus a size I9/5.5 MM crochet hook (or size needed to get proper gauge). I used Bernat Super Value yarn in the color Soft Grey which is an acrylic yarn. If you prefer wool I highly suggest Malabrigo Worsted Merino which has about the same thickness.