The original pattern is for a baby hat, but it can be made in a variety of sizes. For worsted/aran weight yarns I use a size K crochet hook and for lighter worsted/DK weight yarns I use a size I hook. You can make this hat into any size you want by working more or less increased rounds. I usually use 11-14 stitches for the base of the earflaps.
The hat can be made with or without the ears.