The Filter NC (Neutral Clear) from Nikon is a clear (colorless) filter for color as well as black and white films. Also serves as a permanent lens protector. Multi-coated to minimize reflection at the filter surfaces which reduces flare and ghosting.

This filter has no affect on the color of your image but will guard against scratches, dust, dirt and fingerprints from contaminating the fine optics incorporated into the lens. The value of such a filter has been well-documented. If you should accidentally break the filter, that's one thing but if you break the front element of your lens, you'll need a new lens. Some people refer to this kind of filter as relatively "inexpensive insurance".