Stack & Grow 4 Extra Trays -Sand- Add to Stack & Grow Garden Planter To Stack Higher for Vertical Gardening 4 Extra Growing Trays for the Stack & Grow Stacks up to 8 trays high when combined with Stack & Grow Indoor / Outdoor Use - All Season - 1 Year Limited Warranty Collapses for Easy Storage - UV Protected Durable Plastic - Available in Five Colors