Zareba IWSD-Z Wood-Post Self-Drilling Porcelain-Look Insulator, White Large, durable, screw-in insulator for use with electric fencing Can be used with steel wire, aluminum wire, polyrope, and polywire (not recommended for polytape) Easily installs with a power tool in just 10 seconds White with a porcelain look; as strong as steel, more durable than porcelain Measures 1-4/5 by 1-4/5 by 5 inches; weighs 3-2/5 ounces