Powder coated aluminum “Side Mount”. Can be used to mount on the side of a boat dock, wood deck, retaining wall, tongue of a trailer, or other vertical attachment locations. Does not include any hardware to attach. Comes with a sleeve to fit a 3″ diameter flagpole. Don’t forget the Reducer Sleeve for Mounts if your pole is the 15′ or 20′ LT (2.5″ base). The holes are 3/8″ in diameter. From side to side, center of holes are 5 3/8″ apart. From top to bottom, center of holes are 7 3/16″ apart.