Carl Zeiss Jena Flektogon 4/25 is a wide-angle prime lens for Exakta SLR cameras.
Lens in pictures is with M42-EOS mount adapter attached.
Weight is for M42 lens model without caps and adapter. Adapter M42-EOS weights 108 gr.
Lens length is also for M42 model when focused to infinity. When lens is focused to closest focusing distance length of the lens will extend for 6.30 millimeters.
Distance scale close focus distance is 0.20 meters but in reality lens can focus to about 0.18 meters.
Lens mechanical quality:
I gave 3 stars for mechanical quality but that is not fair assessment considering that my copy is about 50-53 years old and seen a lot of usage. Only problem with it was broken part for automatic aperture which is not in use on my Canon 7D anyway. Fix was simple manual aperture control is working properly. Hope that someone will rate mechanical quality with more stars so average score will improve.