Wet and humid conditions have always challenged photographers and videographers. The GoPro HD Hero Camera is no exception. And though it's safe inside its own waterproof housing, there will always be air trapped inside with the camera. If that air is moisture laden, a drop in temperature may cause fogging of the lens inside the housing. That's why the designers at GoPro left a bit of space on either side of the camera to allow for the placement of these Anti-Fog inserts. We don't know exactly what they're made of, but we assume they act like silica gel dessicant and literally suck the moisture from the air inside the housing. They can be re-used up to 5 times by baking them in the oven for a few minutes to drive out any accumulated moisture.