Nikon Eyepiece Cap. D5100 and similar models.

Made for the D5100 camera. But will probably fit lot's of other Nikons. Just measure the naked viewfinder and if it is 24mm...ish across then this will probably fit.

These things are just a simple cap to cover the viewfinder to stop ambient light from leaking trough the viewfinder. Good for those long exposures.

I misplace or lose these all the time. It is just a simple piece of plastic so why fork out money for these when you have a printer?