The EP-N Hydrophobia Eyepiece for Select Nikon / Pentax DSLR Cameras from Think Tank Photo is a required watertight accessory for your Hydrophobia rain cover. It allows you to see through the camera's eyepiece once the rain cover is installed. The slide-on EP-N eyepiece is CNC machined out of Delrin acetal resin and features high-density foam padding.