What’s the difference between a Single Lens and Double Lens?Updated a year ago

Single lenses are the classic most cost effective option, mainly used by ski racers. The product is a single sheet of polycarbonate with a  single color tint, they have a slightly shorter lifespan than the double lens, and are only available in cylindrical form. Double lenses are more durable, have more color variations, and have stronger anti-fog properties. They are 2 different sheets of polycarbonate connected together by a foam spacer. The outside lens takes on the elements while the middle space serves as a thermal shield to ward off fogging.