Thank you for viewing. Nikon genuine eyepiece diopter correction lenses. -2.0D Large 1, Small 2 -3.0D Large 1 -4.0D Small 1 The large ones are for F series, and the small ones are likely for the FM series. Both the large and small ones have the same thread diameter and pitch. Attaching a large one to an FM series camera will prevent the back cover from opening. These are old items, so there are some minor scratches.