Why your outdoorsy friend suddenly has a gummy bear power bank

Why your [ultra-light hiker] friend suddenly has [the world's lightest] power bank.

I remember Colin Fletcher, years ago, writing in The Complete Walker about trimming the borders off his paper maps to save weight, which seemed like an insane over-optimization to me. But then, I'm not an ultralight hiker.

I am impressed folks are getting their loads down to 10 pounds though.

That insane over-optimization is how folks are getting down to (and below) 10 pounds.

I'm not even remotely an ultralight backpacker, but I do count ounces (no matter what your weight limit is, you can't escape making tradeoffs to stay within it). Your hiking load is a great example of how quickly apparently insignificant quantities can add up. Saving fractions of an ounce multiple times gets you large savings far more quickly than you'd think.