Wood ceiling collar allows Iolite new construction housings to be installed in wood ceilings up to 2" thick. Compatible Housings: NHIOICD-48, NHIOICD-415, NHIOICD-420, NHIOICD-425, NHIOICDCP-48, NHIOICDCP-415, NHIOICDCP-420, NHIOICDCP-425 Compatible Trims: NIO-4RC, NIO-4RG, NIO-4RNB, NIO-4RNDC, NIO-4RPH, NIO-4RPHA, NIO-4RSL, NIO-4SC, NIO-4SG, NIO-4SNB, NIO-4SNDC, NIO-4SNDSQ