This is a medium sized 4 leaf barndoor set for a Desisti Leonard 5K Fresnel or Leonardo Piccolo 10K Fresnel Light.
Barndoors narrow the beam spread of a light fixture. They help create a 3-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.