Sizes 3, 4, and 5 are not the same, there's .25mm difference in them which is .5mm between size 3 and 5. Are these going to be used for knitting socks? They're a little large unless you're going to use sport or dk weight yarn; most socks are knit with size 1 or 2, sometimes 3s. A set of skewers might be closer to 1s or 2s. But you need a needle sizer or calipers to measure them more accurately.
sue- knitting heretic