As part of your grow equipment, this is the easiest way to move a second or third indoor garden light all from your one LightRail Motor. Compatible with your existing LightRail 3.0, 3.5, 4.0 or 4.20 system, the Add A Lamp Kit allows for extended coverage for an additional light along with adjustable run length and grow light spacing. The Add A Lamp Kit includes a two-piece, 2 meter Rail (6’6” total length), a 6’ push/pull rod, an Auxiliary Trolley, hardware and instructions. It comes complete. Note: Up to three lights can be moved in-line with this system. For the three indoor garden light configurations, you would have an Add-A-Lamp Kit, then a LightRail 3.5 or 4.0 Kit then another Add-A-Lamp Kit. For moving two indoor grow lights in-line, you would have a LightRail 3.5 or 4.0 Kit and then an Add-A-Lamp Kit. Note: The LightRail 4.20 Kit comes with one Add-A-Lamp Kit included.