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Википедия говорит:

Type I
The black pairs, sometimes called Mickey Mouse boots, weigh 44 oz. (1.25 kg) apiece and are rated for temperatures down to -20°F (-28.9°C) and is made with oil/diesel resistant rubber. They are less common than the white pairs that give the boots their name.
Type II
The white boot is designed for use in extreme cold weather from -65°F (-53.8°C) . It also is a little bigger and heavier (~8 oz. (0.22 kg) per boot) than the black boot because of the extra insulation.