This is a Half Double Scrim for the LTM Prolight 575W HMI Fresnel, Cinepar 1.2K HMI, or any other fixture that accepts a 9" 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.