Eclipse glasses

Eclipse Glasses are a gadget invented by the Mechanist. They first appeared in "The Day of Black Sun, Part 2: The Eclipse".

Description
Sokka commissioned the Mechanist to produce these special glasses so that when the invasion force invaded the Fire Nation on the Day of Black Sun, they could observe the eclipse safely as a means of keeping track of time. The glasses are made of leather, and although they are referred to as glasses, they don't actually contain any glass. The slits block the sun's glare while still allowing the wearer to see. They are reminiscent of eyewear used by some desert cultures to reduce glare and offer protection from sandstorms. The Sandbenders in the second book are seen wearing similar eyewear. The Mechanist produced dozens, if not hundreds, of these glasses for the members of the invasion force. The only ones who didn't wear them were Aang, Sokka, and Toph, who were searching for Fire Lord Ozai in the Fire Nation Capital's underground bunkers.

Trivia

 * The glasses are based on similar specimens created by the Inuit for the same purposes as in the series.