Most of the lenses are concave meaning that they can increase the heat intensity of the sun and may start a fire or hurt eyes if placed to close to the face or flamables. Please be aware of this when placing in windows or using outside.
Most of the lenses are concave meaning that they can increase the heat intensity of the sun and may start a fire or hurt eyes if placed to close to the face or flamables. Please be aware of this when placing in windows or using outside.