Greenbo XL railing, deck rail planter windowbox Color - white - Set of two units 100% SECURE AND SAFE - The Greenbo patent-inner rib mechanism acts as an anchor, thus making sure that regardless of the railing shape, the Greenbo XL rail planter will be fully stable. (No additional component is needed to make it stable). Also, the pot/window-box weighs over 4 pounds. Its thickness along with its 10 sink length makes it perfectly safe to handle windy environments and high altitude. FITS ANY RAIL SHAPE AND SIZE - Compression fit design works with any type (metal or wood) or shape (oval, square, round) of rail whose size is between 1" to 6" deck rails, patio railings and fences 100% WEATHERPROOF  The Greenbo XL Rail Planter is made from durable, weatherproof resin construction. It can resist any kind of weather, as well as the harsh temperatures of summer and winter. Unlike other rail planters, this resin planter won't crack when exposed to extreme weather conditions. SUPERB DRAINAGE - The Greenbo balcony rail planter has two built in draining trays, and therefore the plants roots are completely separated from any water-remains. EASY INSTALLATION-Self-mounting -- no screws, brackets or other hardware necessary