Hothands Insole Foot Warmer 20 Pair Value Pack

How are these one size fits all?

Why does the title have 20 pairs, but the picture says 5 pairs? Are there four packs then for the $38.37?

what is the expiration date on these warmers?

Every single package of HotHands warmers has a year and month of expiration. What are the expiration dates on these?