The irises are used to get more deepsight if the lens is corrected with a strong addition fort he rear sight.
The iris will clip on the backside of the lens holder, also between the eye and glass.
Art. No. 42024 – 42 mm – left & right
Art. No. 32024 – 32 mm – left & right
Art. No. 25024 – 25 mm – left & right