Hubbell-Raco 6244 Nonmetallic Round Floor Box Adapter Ring High strength rigid non-corrosive PVC construction Accepts plastic and metal covers Required for 5511 floor box Gray color Note: RACO Nonmetallic Adapter ring is for use with RACO nonmetallic round floor box number 5511. This adapter ring is suitable for use with all nonmetallic and brass flanges. The adapter simply fastens to the 5511 floor box with the included retaining clips and screws. The clips slide into the molded slots in the box wall