Unique concept extends the typical laser “dot” into a brilliant laser line for greater signaling and search coverage. Operates for 40 hours with common Lithium CR123 battery (included). Use in the same manner you would a signal mirror, but add a slight scanning motion. Effective up to 20 miles at night and 3 miles in daylight. Waterproof, nonflammable, and safer to store or use than flares.