The interior and exterior rotary laser level is accurate to 1/4 in at 100 ft. It is constructed to withstand rugged jobsite conditions with a durable rotary cage that helps protect the head if dropped. an innovative configuration of multiple thin struts maintains the unit's strength while eliminating blind spots. the unit is self-leveling in horizontal mode and in vertical mode, arrow buttons used for manual leveling are more intuitive than traditional knobs. sharp and bright, the beam can be seen up to 100 ft indoors and can be recognized at up to a 1200 ft Dia outdoors with the included detector. the laser also offers a weather-resistant housing for durable and accurate performance. DeWALT® Rotary Laser Level Kit, Heavy Duty Self-Leveling, Bare Tool Bare Tool/Kit, +/-1/4 in Accuracy, 100/600 ft Measuring, +/-5 deg Auto Leveling, 1 Beam, Red Beam, 635 nm Wavelength, Laser Class: 3A, 23 to 122 °F, D Alkaline Battery, Plastic Housing Material, 7-7/8 in L x 9-1/8 in W x 8-1/4 in H Dimensions