9.5"W x 8"H Dovetail Woodworks railing planters fit a 6"or (with added spacers supplied) 4"railing, but you're not limited to just railings.Use your imagination and you can make any area come alive with plants, in the house, on the deck, patio, or along a driveway. With the variety of sizes you can create borders or corners to give any area a finished touch. Planters are of Western Red Cedar, and Hardwood Dowels are used to join all the slats together.They come complete with a sturdy plastic liner (with holes you can punch for drainage) so just fill with soil and plant your favorite flowers or herbs.