4-leaf barndoor, black/silver (168mm/6.6'')

This is an Arri 4 Leaf Silver Barndoor Set for the 650 Watt Compact Fresnel. 

Barndoors narrow the beam spread of a light fixture. They help create a three-dimensional look to a lighting scheme by placing light in a specific area, or by keeping it away. The more leaves a barndoor set has, or the longer the leaves the more precisely the beam can be controlled.