Johnson Level 40-6544 Electronic Self-Leveling Horizontal/Vertical Rotary LaserGreen beam is 400 percent more visible than red beam, Electronically controlled dual slope feature, Electronic self leveling horizontally and vertically, Laser beam modes include dot, two adjustable line lengths and two rotational speeds, Two rotational speeds: 200 and 500 RPM, Visual and audible alarms when beyond leveling range, Height of Instrument Tilt alarm function ensures product accuracy. Green beam is 400% more visible than red beam