This is an accessory Red Lens for the MF Tactical Sierra-P flashlight. This color filter lens easily replaces the standard clear lens. Just unscrew the flashlight bezel, remove the clear lens, replace with the color lens and replace bezel. This lens is made of hardened mineral glass, which is resistant to scratching or breakage. It will also outlive and outperform similar products made of plastic.
A red filter protects your night vision. Under low-light or no-light conditions using white light can impair your night vision for up to a full hour. Using a red lens reduces this affect, allowing re-adjustment to full night vision in just a few minutes.