Laser levels for exterior work such as grading, underground utility work, site preparation, construction stake-out setting forms for pouring concrete foundations or slabs, etc. Typically a Rotary Laser Exterior Kit includes a Tripod, Grade Rod, and a Laser Detector. Laser Detectors are required if working outdoors since most laser beams are not bright enough to be seen by the naked eye outdoors. Also, the use of a laser detector will usually almost double the range of a rotary laser. Detectors can be purchased separately if a laser kit does not include one, but remember to buy a red-beam detector for red-beam laser levels, and green-beam detector for green-beam laser levels as you cannot mix-match detectors.