A Cast Guard Unit (CGU) light fixture is suitable for dry and wet areas and seals a wiring cavity using a single O-Ring. A cylindrical projection of the CGU center telescopingly engages a cylindrical cavity in the CGU top to varying depth and flanges on the CGU center and CGU top sandwich a light shade. The engagement of the cylindrical projection into the cylindrical cavity is free to vary to accommodate varying thicknesses of various light shades. The O-Ring resides between the cylindrical projection and the cylindrical cavity sealing the wiring cavity.