I usually knit everything in the same needle size. However, if you should wish to tighten up the ribbing, use 5mm needles. ChiaoGoo has a 5 mm 9 inch circular needle. In the picture, the ribbing looks very loose. When the beanie is worn, it is not loose.

As the pattern suggests, as well, if the wearer’s head is tall, one should add another 5 rows before the decrease section.