A recessed lighting fixture providing illumination from a light source including a plurality of light emitting diodes (LEDs) wherein the fixture is placed within the ceiling space above a ceiling panel or wall. The fixture has a low aspect ratio heat sink. An interchangeable trim ring has an integrated light reflector and attaches to the bottom of the heat sink via rare earth or super magnets. A flange of the heat sink and a flat annular surface of the trim ring engage each other, providing a large contact surface to enable conductive heat transfer. The flange and flat annular surface are located below the ceiling panel, which is at room temperature to help cool the recessed LED lighting fixture through radiation and air convection.