These needles come in a set of 5 needles (6 inches long), just like your double pointed needles for socks and mittens. The difference is that they have a smooth side (like a knitting needle) and a hooked side (like a crochet hook). They are used in countries like Turkey, Egypt, Peru and Portugal, where the Portuguese Style of Knitting is most common. You do not need this kind of needles to knit Portuguese Style. You can use any regular needles you might have. There are more advantages than disadvantages in using these needles, like anything else. Advantages: 1) you might combine knitting and crochet in the same fabric; 2) You use the hook to pull yarn though stitch; 3) You bind off using single crochet Disadvantages: 1) It is better that you work circularly
These needles have been used for thousands of years and they are really well made in aluminum. If you have any questions about this product, please send me a convo.