I use the MH kit and it’s superb. Just come back from two weeks flying in the Alps and one medium-sized O2 bottle lasted for the whole trip - and that’s in a 2-seater.
You just fit the cannula, turn on the electronics and leave it for the rest of the day. When you’re flying half a wingspan from the rock at 12,000+, you need your blood nice and saturated to keep your brain working properly.
You can fly without supplemental oxygen up to quite high altitudes but the degradation in your performance is real and there are possible long-term effects with damage to the oxygen-starved bits of your tissues...
