I ordered the Tifosi Slip from Zappo's when I was commuting in the winter & my Nike sunglasses were fogging up like crazy:

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The vented lens design really works well, both in colder weather and in hot weather (though when it was 5 degrees and snowing I had to resort to ski goggles...). They're comfortable too, and a great deal -- $50 for decent frames, 4 interchangeable lenses with decent optics (in rose, yellow, smoke and clear), and a sturdy case. Okay so they're not as stylin as Smith's, Oakley's, Rudy's etc but I think they're a good buy.