ISMR4000P 3 Inch Low Voltage Chicago Plenum IC New Construction Housing is suitable for insulated ceiling applications and damp locations. Below ceiling accessible. Takes up to 7/8 inch ceiling thickness. Low voltage 12 volt magnetic transformer is included. One 20 watt, 12 volt GU5.3 MR16 bulb is required, but not included. Dimmable with a low voltage magnetic dimmer. Consult bulb manufacturer for dimmer compatibility when using LED bulb option. Suitable for damp locations. UL listed. 3.25 inch ceiling cut out. 15.5 inch length x 10 inch width x 7.1 inch height. A complete fixture includes a housing and trim, sold separately.