LYKKE 20cm (8") Driftwood Double Pointed Needles, or DPNs, are available in a broad range of sizes from 2mm (US 0) to 9mm (US 13) as a pack of five. They're marvellous for knitting socks, mittens, gloves, hats; anything that you'd knit 'in the round'. They're very handy when you need to knit tiny circumference tubes, like the thumb of a mitten.
As a prolific hat knitter, I use circular needles and then shift to DPNs to decrease for the crown. If you need some circulars to go with your DPNs, you can find those here.