RTFM- if I had a dollar for every tech call I've had that came down to reading the directions, I'd be rich. The same applies to any kind of gear- at least the items is the PSP are hard to use wrong, and there are directions, but in the field is not the time to find out you have the the one-in-a-million oops from AMK, or that you can't use your gear.

And Night raises a good point- don't plan on being peak when you need this. I always assume that I'm going to be soaking wet in zero-ish temperatures with a good wind going, along with either a mild concussion, a broken arm, knee damage, or any combination of the three to go along with my hypothermia. :P