Glacier Goggles for trekking, climbing and skiing in the Highlands, the alps and greater ranges on wild days.
Category 3 will be fine for most uses but for prolonged exposure at very high altitudes (eg expeditions) or for those with weak eyes, Category 4 is preferable.
Categories 0, 1 and 2 are mainly applicable to white out conditions where the reflected glare off the snow is minimal, exactly the sort of conditions one is likely to meet in a full on Cairngorm Plateau blizzard.
By far the best choice for everything from alpine climbing and skiing to prolonged exposure on the world's highest peak are Reactive (Photochromic) Goggles, as the lenses automatically adjust according to the light conditions. Thus they can also be used both in the alps and a Cairngorm blizzard in minimal light. Category 1-3 Photochromics are ideal for this sort of use.