I have heard different opinions on the dpn length for socks. I am using 6" ones. I took a sock class at my LYS last weekend, and the teacher said that the 6" ones are easier to use because the extra needle length doesn't get in your way, like if you were using longer ones. One woman at the class was having a hard time keeping her stitches on the needles, and so she switched from 6" ones to longer, and said it was easier for her- she didn't worry so much about losing the stitches. I like the 6" ones. I haven't seen smaller ones, though. I'm not sure what you'd use them for. Fingers on gloves, maybe?