Fits the classic f series nikons f f2 f2s photomic fa fe fe2 fm fm2 f3. Produced by nikon in the 1970's, this beautifully made eye piece magnifier screws into the eyepiece of a nikon or nikkormat or photomic series finder and magnifies the central part of the viewfinder image 2x for pinpoint precision in focusing. It has a built in diopter correction adjustment to correct for individual eyesight from -4 to + 2 diopters.