This is a white egg crate for the Arri X Ceramic 250W Fixture.
Egg crates are essential accessories for any lighting system. A white egg crate narrows the shape and slightly softens the light output from your light fixture. Consider an egg crate as a painter would a brush, or a sculptor would a knife, or chisel.
An egg crate 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 egg crate mounted on a light fixture will limit the spread of light to 40° from the face of the fixture.