This is a Snoot for the Altman Shakespeare Ellipsoidal spotlight.
Snoots, barndoors, grids, and filters are essential accessories for any lighting system. These devices alter the shape, intensity, or color of the light output from your flash heads. Consider them as a painter would a brush or a sculptor would a knife or chisel.
Use of a snoot will result in a small circle of light when it is attached to the front of your light source. The size of the circle of light will be determined by the opening of the snoot, its length, and the distance of the subject.