True, but you can go ghetto and use some cable sleeve (spiral wrap) or some copper (other?) wire on the ouside to give the same effect. I've seen another type of those "cool sleeves" (product) but fitted in the tube wall itself (part of the tube ). No link. Dunno where it was. Or you could just use a spring to do the same , on the inside of the tube (just make sure it's copper , corrosion is a nasty thing), similar to the electrician's method of bending pvc pipes (hate it, had plenty of experience on that a few years back). Anyway, just a few ideas.