Abstract: A lighting fixture is convertible for selective use in different suspended ceilings having grid members with bearing surfaces of a predetermined height differential. The fixture comprises a housing including a main section and two longitudinal side sections releasably securable to the main section. The main section carries a fluorescent lamp(s), and the side sections carry a shielding media, such as a deep cell louver assembly or a luminous element. The side sections carry tabs which are selectively insertable within either of two vertically spaced rows of slots in the main section to enable the main section (and the lamp) to be vertically adjusted relative to the side sections (and the shielding media) in order to maintain a prescribed photometric relationship between the lamp and shielding media, regardless of which grid suspension system is utilized.