Glacier Goggles for trekking, climbing and skiing in the alps and greater rangers 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 ski-ing to prolonged exposure on the world's highest peak are Reactive Goggles, as the lenses automatically adjust according to the light conditions. Thus they can also be used in a Cairngorm blizzard in minimal light.