Eye bolts consist of a loop at the end of a threaded bolt. The loops are used as anchors for ropes, cables or chains. Some eye bolts feature the ability to pivot or swivel. Eye bolt thread sizes are available in standard inches and metric millimetres. Common sizes in standard measurements range from ¼ inch all the way to 2 ¼ inches in diameter. Common sizes in metric measurements range from 6mm to 54mm in diameter, and are available in 1mm increments.