A luminaire accessory is provided. A first louver part (16) has a plurality of cells (18) arranged in a predetermined pattern and has at least one set of alignment features. A second louver part (16′), unassembled is identical to the first louver part (16). When assembled, the second louver part (16′) is rotated 180° with respect to the first louver part (16) and the alignment features (20) are configured to mate to a second set of alignment features (20′) disposed on the second louver part (16′).