Scotty's #1027 Rail Mounts fits up to a 1-1/2" round rail or oval-shaped wooden rails. It is easily installed and removed for storage. The wooden board (not included) transfers the downward pressure to the boat gunnel. Fits all Scotty downriggers and can be used with Scotty's 1026 Pedestal Swivel Mount. Dimensions: 6-1/8" x 7-1/8".