4 Square Chicago Plenum Air Tight Extension Ring, 2-1/8 in. Deep, 1/2 & 3/4 in. Knockouts

Chicago Plenum, 2-1/8 in deep, 4 in square drawn extension rings with air tight (8) 1/2 in & (4) 3/4 in conduit knockouts are added to Chicago plenum 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 space is needed. Bottom mounting slots allow a quick installation onto existing boxes.