Available in halogen and LED versions, the 4 inch Surface Mount Fast Jack canopy mounts to a standard 4 inch electrical box with plaster ring or an octagon box. The 75 watt 12 volt electronic transformers (included) or 60 watt LED power supply fit inside canopy. Halogen version is dimmable with electronic low voltage dimmer. LED dimming range varies: reference corresponding fixture specification sheet, at www.edgelighting.com, for dimming details.