Think Tank Photo EP-20 Hydrophobia Eyecup/Eyepiece for Canon and Olympus EP-20: Hydrophobia eyepiece fits the Canon 5D MarkIII, 5D MarkIV, 1D MarkIII, 1D MarkIV, 1DX, 7D, 7D MarkII, Olympus E3 and E30; CNC machined Delrin eyepiece with high density foam padding. Replaces View finder hood, enabling waterproof protection for your camera when using Hydrophobia rain covers. Remove the cameras eyepiece by sliding it upward and off the viewfinder. Align the groove on the EP-20 with the rails on the cameras viewfinder. Firmly slide the EP-20 down on the viewfinder rails until fully seated.