Start with the grow lights you need now, add more as you need them. Each Stack-n-Grow Light unit has two 3' long, full-spectrum T5 fluorescent bulbs that are spaced for optimum light coverage. High-tech reflectors direct light down onto plants for healthier growth and less glare. Start with the Stack-n-Grow Light System, and then place Add-On units on top to multiply your growing space. Add-On units include wall brackets for additional stability. Fast, no-tools assembly Start 72 seedlings in 3-1/2 sq. ft. of space Shown with our GrowEase Seed Starter Kits, sold separately Easiest-ever system for adjusting light height Lightweight - each unit weighs just 7 lbs. Stack up to 2 add-on units on top of the base unit Stores compactly in the off-season Important: When stacking units, prevent water from dripping from upper shelves onto the light fixtures below by placing our Small Boot Trays (32-709) underneath, or use other drip trays or saucers on each shelf.