You will need: worsted yarn in two colors, main (up to 100 grams for the largest size) and brain (up to 150 grams for the smallest size, up to 220 grams for the largest size), and knitting needles to obtain the gauge (for knitting in the round), a stitch marker, a darning needle, a small amount of waste yarn.

Gauge: 19 sts in 4 in / 10cm in stockinette stitch. Row gauge is not important for this pattern.