I used Red Heart Super Saver (#4) yarn, but any #4 yarn will make a good substitution, just make sure you get the exact gauge as stated in the pattern when you make a sample swatch. If your gauge is bigger than stated, go down one size in your hook. If your sample gauge is smaller than stated, go up one size in your hook.
Bonus Pattern: Super Fun! Super Silly! 1960’s Inspired Belt Free Crochet Pattern