I would call this size, one size fits most. It is good for me and my daughter, though I do have small hands.
What you will need:
Super Bulky Yarn (6) I used Yarn Bee Soft Illusion.
hdc-half double crochet
sl st-slip stitch
Row 1: 1 hdc in 2nd ch from hook and each ch across. Ch 1, turn (22hdc)
Row 2-18: 1 hdc in each st across. Ch 1, turn. (22hdc)
Do not fasten off.
Once you have finished your last row, bring your sides together.
Ch 1, sl-st sides together evenly across.
Fasten off and weave in ends
Sc in 2nd ch from hook and each ch across.
Slide the cord through the muff (taking care to not twist ch) and join with first sc.
Fasten off and weave in ends.