This page contains expedition, alpine and ice-climbing boots designed primarily for climbing and, though most climbing involves a considerable element of walking, these are not boots to consider if you solely want a walking boot.
Usage: We are often asked "Is this boot suitable for Rum Doodle?", or somewhere of that ilk. Beyond the obvious, ie that a thin 3 season leather boot is not going to keep your toes warm on Everest, it is hard to be precise on this issue. Some manufacturers are cautious and so may undersell the capabilities of their boots, while others may do the opposite. The way the boot is fitted makes a big difference too. A relaxed fit, with room inside for a medium thick sock, plus a thick mountain sock, and room to wiggle your toes will make a boot a lot warmer than fitting half a size lower and just having room for the mountain sock. Use of an overgaiter increases the warmth. Finally people feel the cold differently. With all those factors in mind we have given an approximate idea of what each boot is capable of - but it is only a guide. Standard plastic boots have been used on many successful Everest attempts and modern leather boots have been seen on top of Aconcagua - so often you can get away with things that the boots weren't really designed for. At the same time, you might meet with considerably colder temperatures than normal - so it is wise to be cautious. Ultimately there is no 100% correct foolproof answer.
Scarpa give good advice on fitting boots and shoes in the film below: