City Theatrical Top Hat for Short D-60.
Top hats serve two functions in entertainment lighting - to control light spill or to reduce the viewing angle to the lens. Sometimes poor fixture optics or poorly maintained lenses can cause light to be directed into the audience or onto scenery, and top hats can help control that. It is also objectionable to the audience or camera to see the bright source of the light and top hats can shield the bright source from view.
Specifications (refer to diagram):