Recessed 4" square aperture specification grade luminaire utilizing a field replacable LED array conforming to Zhaga standards for interchangability. Lamp modules and optical elements may be changed after installation providing a variety of light sources and optical distributions. Housing is suitable for 2x8 residential framing or commercial installations, suitable for direct contact with insulation and is airtight to prevent energy loss, room drafts, dust marks on the ceilings and reduces sound transmission. A complete luminare consists of a housing platform, lamp module and optical element. Use where high efficiency, excellent light control and low aperture brightness are demanded.