The Classic Deck Rail Planter by Bloem helps make the most of your porch or patio living space. Grow a mini garden in an elevated space, ideal for house and apartment use. Compression design fits rail size 3.75" or 5.5" wide. It is also compatible on railing widths slightly smaller (3" up to 3.75" or 4.75" up to 5.5"). For smaller rail sizes, we recommend securing with screws or zip ties under railing for added stability. This planter is designed to maximize growing space and features a tiered bottom design, allowing dirt and roots to grow strong and deep.