I love these Light Saber knitting needles.
Some quick calculations (hopefully, I have done this right), means that the 3/8″ lucite rod will yield needles that are roughly 9mm/US 13. It seems like you could make smaller sizes as well. However, I think making circulars (my preferred way to knit anything, including flat pieces) might take a little more doing.
I love the idea of being able to knit in bed without having to turn the light on, though. It’s the knitter’s equivalent of the Itty Bitty Booklight.