These were the mountaineer's power bar of yore and carried Sir Edmund Hillary and party to the first successful summit of Mt Everest.
My best buddy Chris Nellis and his wife Cheryl sent me enough of these for Xmas to power me through all the ice climbing and mountain summits I still have left in me.
Really excellent! Like a large, soft, chewy and well-behaved Altoid. And given its role in the first summit of Everest in 1953, it's going to remain edible and chewy at temperatures that turn a Power Bar into a titanium ingot.
And the tin it comes in has a million cool uses.