This is a Medium, 1/2" Black Eggcrate for the Desisti De Lux 4x55W fluorescent fixture.
Egg crates are essential accessories for any lighting system. An eggcrate alters the shape and intensity of the light output from your light fixture. Consider an eggcrate as a painter would a brush, or a sculptor would a knife, or chisel.
An eggcrate is a rigid, or semi-rigid plastic or metal grid that narrows the spread of light. The spread of light will be determined by the density of the honeycomb mesh, and the distance of the subject from the light. Unless specified otherwise, an eggcrate mounted on a light fixture will limit the spread of light to 40° from the face of the fixture.