FURTALKPonytail Beanies for Women Messy Bun Winter Hat with Tail Hole Cotton Lined Knit Skull Beanie Outdoor Runner Cap

What is the difference between one size and medium?

Is there any chance that I got wrong size? I order Medium, but it is too big!

Does this cause lots of static in your hair? I work in a really dry but cold environment in the winter, and sometimes static is an issue- thanks

Is medium smaller then one size fits all?