The Grid for 18" Round LED Full Moon Light from Genaray allows you to add directional control to the Full Moon Light. The rigid grid clips quickly and easily onto the fixture, eliminating spill light and tunneling the light forward to narrow the Full Moon's beam spread from a wide 120 degrees to 40 degrees. This enables selective lighting that allows you to light areas that you want to, and keep light from areas that you don't want illuminated. Genaray RSF-18-GRID Specs Dimensions: ø: 18.0" / ø: 45.7 cm Package Weight: 1.73 lb Box Dimensions (LxWxH): 19.0 x 18.3 x 2.2"