Waterproof eyepiece required for use with Think Tank Photo Hydrophobia rain covers. Compatible eyepiece (EP) for Nikon screw-in eyepiece mounts. Fits the D5, D4, D4S, D3S, D3X, D3, D810, D800E, D800, D700, D500 and others. CNC machined Delrin eyepiece with high density foam padding.