HARCO 60-100-03 3" Ductile Iron IPS Knuckle Joint Restraint - The Knuckle Joint Restraint by HARCO provides an easy to use, economical option for thrust restraint of HARCO small diameter push-on ductile iron fittings for IPS-PVC pipe. The unique, two-piece design handles as one piece and permits a one-bolt actuation. The restraint is mounted on the fittings so that the bolt is accessed from the top, making for ease of installation and inspection. Mechanical serrations in the grip ring assure proper gripping of the pipe. No restraint rods or bolts are required.