Heavy Metal interchangeable needles, by the same folks who produced those handmade wood interchangeable needles I was so thrilled to get a while back. These are the same design, but executed on a much tinier scale in solid stainless steel (most metal knitting needles are hollow and usually aluminum) ... each tip has a threaded end about the size of the screws in eyeglasses and can be mixed and matched with the various lengths of cables. On the serious tools scale these needles are the equivalent of fighter jets built by Rolls Royce. (Or, to put it another way, the Addi Turbos I currently use for socks are Porsches ... Heavy Metals make Turbos seem to handle like elderly plowhorses)
Ruler for scale ... the smallest tips (on the left) are two millimetres in diameter, the largest (on the right) are a huge-by-comparison 3.25 millimetres in diameter. 2mm are the size I use to knit most socks (I got an extra pair of tips in that size so that I can use them in my preferred 2-socks-at-a-time-on-2-circs technique).
Can't wait to give 'em a test drive!