1-1/2" deep, 4" square extension rings with (6) 1/2" & (6) 1/2"-3/4" side knockouts are added to junction boxes to increase wiring capacity and provide access for additional conduit runs and electrical wire. Garvin Industries’ extension rings prevent the need to remove old conduit boxes and wiring from circuits when additional wiring is needed. Their bottom mounting slots allow a quick installation onto existing boxes.