An interchangeable set is the sensible way to buy needles: tips in every size, cables in every length, and one case to keep the lot in.
Twist Red Lace is the stainless steel set – sharp lace tips, and a multi-strand steel cable with no memory in it at all, so it hangs straight instead of coiling up. Spin is the bamboo version, on a clear nylon cable that lets the tips swivel as you work.
Shorties are the ones worth knowing about: 5 and 8 centimetre tips that make up circulars as short as 23 centimetres, for sleeves, hats and anything else too small to go comfortably round a normal needle.