The Think Tank EP-NSI Eyepiece allows users of pro and prosumer Nikon DSLRs to make use of Hydrophobia Covers, which protect cameras and lenses and keep them dry while you're out shooting in all weathers.
The EP-NSI will fit Nikon's D4, D4S, D3S, D3X, D3, D800, D700, D810 and D800E cameras, as well as some others.