This is a Half Double Wire Scrim for the Mole-Richardson Tener 10K, 12K Fresnel, and 12/18K HMI PAR, or any other light that accepts a 21" accessory.
Full scrims dim the light across the entire beam spread, and 1/2 and graduated scrims are used to even the beam spread when lighting a subject or background from an angle.
Keep several densities of scrims available to be prepared for any lighting situation.