The Raised Garden Bed Starter Kit includes (4) stackable corner mounts. These corner mounts hold a 5" high board. Add more Raised Bed Starter Kits to increase the height of the garden. You can also select the size of your garden depending on the length of the boards you select. Simply insert side boards, with a thickness between 11/16" - 1", into the corner mounts. Raised garden beds give you more control over the location of your garden, and allows you to choose the best soil for your particular plants. In addition, they provide more efficient drainage, and gives you a longer growing season because the soil warms up faster so you can plant earlier. Depending on the height you choose, they are easier on backs and knees due to less bending and stooping. Raised beds also provides a strong defense against natural elements.