One size. I originally made this for my daughter who is 5-years-old but you can easily tweak the pattern to fit your child.

Size: 5T
Finished Measurements: when vest is laid flat it is 14” wide and 22” tall.

Notions: buttons are optional if you want it to have a button front.

You will need to know the following stitches:
single crochet
double crochet