Constant red laser beam. Highest power output laser commercially available. Keep all your rail space with a built in extra rail. Small as a matchbox - requires 1.75" of rail space. Super rugged - survives multiple drops to concrete.We even baked it to 350 deg Fahrenheit. Adjustable windage and elevation setting for precise alignment. Maintains alignment through battery changes.Optional momentary activation switch comes in 6 and 10 inch cords.