Shop for Outdoors at The Home Depot. This exclusive mailbox planter, shaped like a Mexican pot, comes in 2 parts that easily slide together around any mailbox post 4 in. square or smaller. Constructed of a blend of natural stone, resin and fiberglass, the planter is lightweight, watertight and weather resistant. The 85% crushed natural outer stone surface ages to a beautiful time worn, old world hue as it weathers. Color: Aged Charcoal.