Ok so got my hands on a new Zippo Heatbank 9s hand warmer. Has a low, medium and high heat setting, and single or dual sides. I topped off a full charge on it, turned it on to high and dual sides. Pleasantly surprised how warm this gets, for sure warmer than the normal chemical hand warmers and warmer than both zippo fuel warmers I have. I expected to get maybe an hour with full blown settings, was going strong at 2 hours and 35 minutes. Granted this was in a warm house but I was very happy with that. It says up to 9 hours, on low one sided, may very well be legit. For me, think I would leave on low and then turn on high to get a good warmup on the hands. It is bigger than the Zippo fuel warmers so probably better suited for a hand muffs. They do make a smaller thinner one rated for same heat but only 3 hour rated. All in all I was surprised.