New DK-17 DK17 Back Viewfinder Rubber Eye Cup Eyepiece Eyecup For Nikon D700 D800 D800E D810 D850 D3 D3S D3X D4 D4S D5 DF D500. No corrective value and are for dust protection only. Select eyepieces are supplied with a rubber coating designed to lessen scratching of a photographer's eyeglasses.
eBay