The Ridgid 66653 3 Chain Penetrating Chain Knocker is optimal for removing grease, scale, light roots, wipes, and other soft blockages. This unit made to be used on copper, galvanized and cast iron pipe with a 4 in. pipe size. Users are provided with a chain knocker that is made of carbon steel and attaches to cable with set screws and a 3mm hex key. The Ridgid 66573 is designed for use with 1/4 in. cable on K9-306 FlexShaft drain cleaning machines (Not Included).