[nwh]

I know you're being sarcastic, but there's probably lots of round aluminum extrusions around to choose from. It would make the thing cheaper to build without having to go and make their own dies, just make two injected plastic ends and you're good to roll.

[Tloewald]

Interesting point (and I hadn't considered this) but a quick search reveals plenty of standard off-the-shelf aluminum extrusions that won't roll off a table and also could accommodate plastic end caps, such as rounded rectangles.

Now they may want a cylinder to maximize underwater performance, but that seems pretty far-fetched. It's just a stupid shape.

[arethuza]

Actually, having a power pack in something like a SIGG bottle would be rather good - at least until you go backpacking and take your USB power bottle rather than the bottle of stove fuel...