NiSi PRO Nano HUC UV Ultra-Thin Filter use a double-sided multi-layer lens technology that incorporates high-quality Japanese optical UV absorption glass. This ensures high light transmission and a very smooth surface that avoids unnecessary reflections. The frame is made of brass with precision threads. The NiSi PRO Nano HUC UV features an exclusive, creative "U" Nano coating and a hardened waterproof coating. The UV filter also serves as a general protective filter that can remain on the lens at all times. Filters help keep dust and moisture away from the lens element and provide additional protection in the event of drops or situations where scratches may occur.