Micro-fiber in the lens has a surface of evenly added layer, when
you wipe the lens, the lens surface forms a uniform layer of
hydrophilic molecular layer. When the lens enter the wet and warm
environment from the low temperature environment, the lens do not
form the mist on the surface of, guaranteeing the lens perspective
effect. With just a wipe, you can get as long as 3 days anti-fog
effect.
http://www.hnf-cleaningcloth.com
Anti-fog Lens Cloth