I have owned this cap for about a decade and used it in four continents. Credit where it is due, this headgear consistently exceeds expectations. How can it be so warm? How is this thing possibly staying on my head in this gale? Wow this thing is light! ... And finally...
How does it manage to fit in that tiny chest pocket in my wind-shirt?
Put all this together and this cap is the best practical means of temperature regulation I know of for backpacking, hiking and climbing. Snuggly warm ear and neck flaps, and a peak that keeps the sun and rain out of your eyes. I have slept in it whilst bivvying in subzero conditions, and the latest version of the Ice cap with press stud might be even better because you can flatten the peak against your forehead. I've never used the chin strap feature.
It's not often you come across the perfect piece of kit - this is only the second time it has happened to me, the other being my pertex+micro fleece windshirt. Everything else is replaceable, but these two items I would immediately go out and buy the exact same model and size without hesitation.