ASME B16.9 Collar A collar — sometimes called a backing ring or Van Stone ring — is a loose steel ring used together with a lap-joint stub end. Unlike a standard weld-neck flange, the collar is not welded to the pipe. It simply slides over the stub end’s lap face and is drawn tight by the flange bolts, while the stub end itself — not the collar — forms the actual pressure-containing surface. This construction lets the pipe spool be rotated freely to align bolt holes on site, which is a major advantage on long pipeline runs, lined-pipe systems, and any project where field alignment matters more than a fixed, welded connection.