This all-in-one success kit includes the whole thing you want to start seeds. With our modular LED Stack-n-Grow Light System, you’ll start with the base unit, and then stack up to two LED Add-On units on top of the base unit to multiply your growing space. Every Stack-n-Grow unit has two 3′ LED bulbs, engineered to save energy and grow exceptional plants. The Stack-n-Grow Garden Starter Kit includes your collection of Base or Add-On Unit(s). Every unit also includes: Three 24-cell GrowEase Seed Starting Systems Two 6-quart bags of Organic Seed Starting Mix 24 seedling markers Add-On units include wall brackets for additional stability. Important: When stacking units, prevent water from dripping from upper shelves onto the light fixtures below by the use of our Small Boot Trays (32-709), drip trays or saucers on Every shelf. About our LEDs: Our product development team engineered these LED light tubes to meet the exacting needs of plants. They deliver full-spectrum light with an additional spike of blue light to stimulate stronger root growth and improve photosynthesis. LED tubes may not shatter like glass bulbs and they are mercury-free so, unlike fluorescent bulbs, there is no need for special disposal. .