Nikon Circular Polarizer
Polarizers look similar to neutral density filters, and they will typically block a few stops of light, but they're fundamentally different: a polarizing filter rotates in its mount to selectively block glare and reflection, which gives you a great deal of control over image contrast and tone, while a neutral density filter evenly reduces exposure without affecting the image balance. Fun fact: a polarizing filter is one of the very few optical filters whose effect can't be replicated digitally. Circular polarizers will work on autofocus and manual focus cameras.
Nikon circular polarizing filters are well made filters with wider-than-usual front glass designed to prevent vignetting (and also, to require proprietary hoods, which are not included)
Image is for illustrative purposes only. Actual item may differ.