If you operate in harsh environments (i.e. the desert) or conduct force-on-force training under NVGs, you need a set of these Protective Lens Covers (aka 'Sacrificial Lenses') to protect the objective lens of your goggles.
The Wilcox Protective Lens Cover is low-profile and secure because it threads onto the objective lens instead of press-fitting over the top. It threads into the interior diameter of the AN/PVS-14 Night Vision Monocular for anti-reflective and scratch-resistant protective cover.
A clear polymer lens and rubber O-ring are surrounded by two aerospace aluminum rings that thread together. The O-ring locks out moisture so the view stays clear. The outer O-ring makes contact with the PVS-14 objective lens housing, further reducing moisture buildup between lenses.
The Wilcox design allows just the lenses to be replaced which is a huge cost saving as sacrificial windows tend to get worn quickly and need to be switched out often. The Lens Cover can also be used in conjunction with other accessories such as a Re-Focus Ring or the factory pinhole lens cap.