Laser beam is aligned to be concentric with the outside diameter of the brass housing. This allows the installer to use the outside of the case for centering and positioning the beam. Projects a vertical and horizontal laser chalk line, Solid brass industrial grade housing protects laser diode - won't rust or spark, Solid glass optics are designed for harsh work environments, Wedge internal prisms steer beam and maintain beam alignment for impact resistance, "O"ring seal - water and oil proof to IP67 standards, Beam-on indicator verifies unit is working from a distance, Accessory parts available include Mounting Bracket (40-6229), Aperture Pack (40-6226) and 70 Degree Fan Angle Line Generator Lens (40-6228), 40-6220 Includes > Red industrial alignment dot laser with 110V AC, instruction manual