Injection Molded Nylon. Designed to fit snugly on a 7/8" round rail without the use of fasteners. The Rail Mount Bow Sockets aid in assembling a rounded support structure for a cover and can be easily removed from the boat when the cover is not in use. Display Pack of 2. Sea-Dog Line is a 3rd generation family company with a history of satisfied customers stretching back to the company's start in 1933. The company is the recipient of multiple industry awards for quality and efficiency.