A lighting assembly includes a heat-sinking housing, a lens, a light source module including at least one LED, and an AC to DC converter to receive an AC voltage and supply regulated electrical energy to power the light source module. The housing includes a closed rear wall and a sidewall that defines a housing cavity containing the at least one LED. The closed rear wall and the sidewall are formed of a heat conductive material to conduct heat generated by the light source module. The assembly has a front end face, and at least one exterior width dimension of less than 3½ inches. In one example, a circular recess defined along an inner edge of the front end face contains the lens in the assembly. In another example, the front face includes a tool-less mating mechanism, for example a twist-and-lock mechanism comprising multiple flanges and/or slots.