The Greatland Lasers are a compact, safe, and effective survival tool for emergency signaling. An expanding laser line appears as a brilliant red flash of light. At 8 miles the line is 3,000' wide and at 16 miles it is 6,000' wide. The H.R. 386 Bill "Securing Aircraft Cockpits Against Lasers Act of 2011" specifically exempts "an individual using a laser emergency signaling device to send an emergency distress signal", so it is legal to use a Rescue Laser to signal an aircraft in an emergency!The Rescue Laser Flare® Magnum is designed to stow away in your survival gear or life raft, but can certainly be carried on you. - Nighttime signaling up to 20 miles. - Daytime signaling 1-3 miles. - Operates 72 hours (on one battery). - Compact - Weighs only 6 oz. - Long life RED laser diode - 10,000 hours meantime to failure. - Limited Lifetime Warranty (by manufacturer). - Operates on Two AA batteries. - Signal duration is equal to 4320 one-minute pyrotechnic flares. - Waterproof to a depth of 80 feet (24m). - Rugged Aircraft Aluminum construction - No Fire Hazard & Environmentally Safe.