on any other Fed lens, except standard 50mm lenses of cause or Tair-3 (not Tair-3FS) lens, or Jupiter-6 lens. My lens is in very good conditions. Included back cup. I also throwing in 85mm viewfinder to compliment this lens. 85mm viewfinder is not exactly made for this lens, but it close enough to use it with acceptable results with 100mm lenses.