Zinc Cotter Pins are used to secure two items together with the use of a common hole. Place the cotter pin in the hole. The bulbous head stops the pin from moving all the way through. Included parts come in 5/16" and 3/8" eye diameter variants and run 2" to 4" in length. Full assortments of #45691 contain six (6) refills comprised of Hillman item numbers #45692 - #45697.