I found these metal rods the other day when I was buying some Chinese lanterns for the lighting kit at the local Ikea. They're made out of a very sturdy hollow steel and my caliper shows them to be exactly 15mm in diameter. Since their intended use is as drawer handles, they're rock solid, but also surprisingly light weight, and come in 5 different lengths ranging from 6 5/16" to 29". (The ones shown are 13 7/8", aka 352 mm.)
It LOOKS to me like they should be perfectly compatible with either a Cavison or Indie rails system, but a search of the posts doesn't show any mention of them before, and since I don't have access to either one of those commercial rod systems at the moment, I'm tossing it out here to see if anyone else can find a use for them. I'll also point out that I bought the black ones simply because they were slightly cheaper than the stainless steel ones... $6.99 a pair... and while there's an old-school baked on enamel finish I like on the black ones, the stainless rods are perfectly smooth.
The one thing that I found really interesting about these is that each rod has a pair of threaded holes in it (only on one side of the tube,) one on each end about an inch and a half from the endcaps. The rods come with little matching pieces of tubing that mount flush to the surface... normally how they're fitted to a drawer, but also ready made method of either securing the rods together or mounting something on them (albeit in a fixed point.)
The brand name is Lansa and while they're a "purchase in the store only" item, they ARE listed on Ikea's web page here: