US 5 (3.75 mm) for curled edges. 2 sizes smaller than size
needed to meet gauge in stockinette, or up to 4 sizes smaller than
size needed to meet gauge in pattern.
US 9 (5.5mm) for Rounds 2-33. Or size needed to maintain
gauge.
US 8 (5.0mm) for Rounds 1 and 34-49. Or size needed to
maintain gauge. Some knitters may be able to maintain gauge
without switching needles.