Nikon Reflex-Nikkor 500mm f8 is a reflex telephoto lens for Nikon F mount. Right off the top, mirror lenses have a few "downsides": they don't have an adjustable aperture, and out-of-focus highlights can take on a donut-like appearance. This lens includes a pair of rear-mounted ND filters to help moderate exposures, so that's at least some help for the first issue; as for the donuts, well, you may just have to learn to like the donuts. The upside is that you get tremendous reach in a small, lightweight package. In addition to the two ND filters, this lens includes the L37c UV rear filter and an orange filter; it also includes the suspiciously short HN-27 lens hood. This lens is the 2m focusing version.