I use heat shrink tubing on the ferrocerium rod of the BSA "Hot Spark" that lives in my keycase (to protect it from the keys and other abrasion). With care, I managed to shrink it just enough (over an electric range, not a flame) so that it's a snug sliding fit, and can be removed and replaced. The excess shrank quite a bit more, to a sort of nozzle shape. Of course, if I ever have to use it a great deal, the rod will presumably get thinner and the tubing will no longer fit... by which time I don't expect I'll care at all. Radio Shack. It comes in handy for a number of things. I try to keep an assortment on hand.<br><br>I was able to find PTFE (Teflon) tubing more or less like that in Doug's kit in an electronics supply store (not Radio Shack). I'd like to find some in longer lengths, but not larger diameter, for setting up siphons. I've been using the thinner variety of aquarium tubing for that in the woods, but it's too bulky to store much length in a PSK. The soft silicone normal-size variety might even pack smaller than the thin vinyl stuff, under compression, since it flattens and bounces back.<br>