The XSearcher head is an add-on for the Night Master 800 and '800-IR models. To use, you simply unscrew the Night Master head and replace it with this one - using your existing LED. It uses a 66mm convex lens, compared to a 50mm lens in the Night Master. This bigger lens provides a tighter beam and more distance. Despite being bigger, there is still sufficient clearance from a scope's 56mm objective lens tube when using the high scope mount supplied in the Night Master 800 kit.