Vigilante sunglasses with interchangeable lenses - Bolle Vigilante Sunglasses with Interchangeable Lenses

This is the most versatile unit i have discovered, short of carrying two pair of glasses. The added lenses, cover a wide verity of uses, plus having all of the lenses in one case lets you change a lenses to cover different times of the day. One drawback, the lenses is sometimes hard to remove.