A light diffusor (12) is disclosed which includes a translucent or transparent light diffusing portion (24) and a rigid mounting neck (25) coupled to the diffusing portion (24). The diffusing portion (24) has an inwardly extending flange (27) with a series of mounting hole (28) therein. The mounting neck (25) has a generally cylindrical, upright section (30) and an inwardly extending mounting flange (31). The neck inwardly extending mounting flange (31) has a series of mounting holes (33). The light diffusor also has first annular gasket (35) mounted between the mounting neck flange (31) and the diffusing portion flange (27), a second gasket (37) mounted below the diffusing portion flange, and three mounting brackets (40) mounted below the second gasket (37). The first gasket, second gasket and mounting brackets all have mounting holes (36), (37) and (41), respectively. A mounting screw or bolt 43 extends through each neck mounting hole (33), first gasket mounting hole (36), diffusor portion mounting hole (28), and second gasket mounting hole (38), and threads into a bracket mounting hole (41) to couple the light diffusing portion to the mounting neck.