The 61mm Slip-On Front Lens Cover for Select Nikon Lenses from Nikon is a replacement front lens cover for select Nikon fisheye lenses. It protects the front lens from scratches, fingerprints and the elements while the lens is not in use. It does not snap into place, but slips on over the built-in lens hood.
AF Fisheye-Nikkor 16mm f/2.8D;
AF DX Fisheye-Nikkor 10.5mm f/2.8G ED
Nikon 61mm Slip-On Lens Cap for 16mm f/2.8 Lenses (Replacement)