The Nikon DK-17C -2.0 Eyepiece is a wonderful addition to the viewfinder that helps in correcting the individual vision. The value -2 indicates that this eyepiece has a diopter value of minus two and will help in correcting the shortsightedness of your vision. Nikon SLR Cameras without built-in adjustable eyepiece correction have a base diopter value of minus one. The value of the eyepiece is a combination of the viewfinder’s diopter value of minus one. Use this eyepiece by attaching it to the viewfinder of your camera and enhance the viewing experience. This eyepiece is compatible with Nikon D-SLRs that feature a circular-eyepiece.