The PVS-14 Sacrificial Window is a must-have item when operating in environments which have a high amount of dust, dirt, and debris in the air (such as deserts with high wind or areas with high storm conditions). The Sacrificial Window snaps over the Objective Lens of the PVS-14 and acts as a barrier to protect it from chips and scratches. It is easily attached and removed and can be discarded or replaced. Please note that you cannot attach the Day Filter Cover when the Sacrificial Window is installed.