The Coghlan's 2" x 3" Laminated Glass Signal Mirror is made of 1/4" laminated glass (two 1/8" glass panels laminated together with a rubberized sealer) that is shatter resistant. The sealer allows even a cracked mirror to function. The unique feature of this Signal Mirror is the center-viewing hole and sight targeting retro-reflective grid. This special feature allows the lost party to direct up to 6 million candlepower of reflected sunlight onto the rescue target with pinpoint accuracy. The glass used is virtually distortion free which allows the reflected sunlight to travel 25 or more miles. This is two to four times further than the light travel from acrylic mirrors. Each mirror has a reinforced lanyard hole and comes in a protective foam pouch. Use directions are printed on the back of the mirror. Measures 2" x 3" and weighs 1.8 oz.