For such a simple design, choose an extra-special, soft and colourful yarn. I’ve knit the hat in 4 different yarns: the smallest shown is merino wool, the next largest is merino/camel, the next size is baby alpaca, and the largest is variegated suri-alpaca/merino/cashmere. Note that the fiber you choose may affect your gauge, which is why I’ve provided plenty of sizes.

Skills required include working stockinette and garter stitch in the round, m1 increase, k2tog, ssk, I-cord (optional)

Sizes: 13 (14 1/2, 16, 17 1/2, 19, 22) inches around, 6 1/2 (7 1/4, 8, 8 3/4, 9 1/2, 10 1/4) inches deep
Yarn: 50 (50, 75, 75, 100, 100) g of worsted weight yarn (approx. 100, 100, 150, 150, 200, 200 m)
Needles: 3.5 mm (US size 5) and 4.0 mm (US size 6) set of 4 dpns or long circular needle for magic loop method (or size needed to obtain gauge)
Other materials: stitch markers, tapestry needle, 1/2“ buttons (optional)
Gauge: 22 sts and rows per 10 cm (4”) in st st.