https://defenders.org/sea-turtles/basic-facts, “Sea turtles are one of the Earth’s most ancient creatures. The seven species that can be found today have been around for 110 million years, since the time of the dinosaurs. The sea turtle’s shell, or “carapace” is streamlined for swimming through the water. Unlike other turtles, sea turtles cannot retract their legs and head into their shells. Their color varies between yellow, greenish and black depending on the species.“

Hat size is determined by hook size
Instructions to make a lining are included
Small G hook (4.25 mm) 20 inches around by 7 inches high
Medium I (5.50 mm) 22 inches around by 8 inches high
Large K (6.50 mm) 24 inches around by 9 inches high

There are pictures of almost every step. the pattern is written in American Crochet Terms