Consisting of QUAD 1000 HDD model for Top-Down laser plumb, as well as HDU Bottom-Up laser plumb. The QUAD 1000 HDD provides a self-levelling downward shooting laser for plumb control while the QUAD 1000 HDU provides an upward (Zenith) self-levelling laser for vertical plumb control, ruggedly built to withstand the harshest environments, with accuracy of up to ±5 arc seconds, long range of up to 600m.