This cup warmer is knit with the cast on edge as long as the cup is tall. If your cup is taller than mine and you want a taller warmer, cast on pairs of extra stitches in the edging (a knit and a purl in the ribbing on each side of the center motif) to get desired size. You can also add repeats of the center motif to make it as long as you need to go around your cup.

One ball of yarn easily makes 2 cozies for average size cups.