We get it. Optics made for hard use get used hard, and sometimes bits and pieces get lost along the way. When you've got the highest quality germanium lenses in the game, it's important to keep them protected with a quality lens cover. Replacements are now available for both our Standard (rubber) style optics and enhanced Tenebraex(C) compatible optics. To determine which style your Fusion Thermal device requires, check the front of the device near the objective lens. If the housing is smooth, you'll need the Standard style lens cover. If it has ridges machined into the housing, the Tenebraex(C) lens cover is required.