Gehmann #501MC Rearsight Iris with colored caps Iris 0.5-4.5mm

501MC Gehmann iris & push-fit coloured rings

Iris 0.5 - 3.0mm
In an attractive, anti-reflective matt silver and blue finish
Laser engraved indications
Steel threaded connection - which for example enables the use of a diopter 
5 external push-fit rubber rings which attach to the knurled ring in: Red, yellow, green, blue and black
Designed to provide an illusory optical effect which ensures perfect eye alignment
An extremely simple and inexpensive idea that gives an exceptional improvement