The system of rear sight irises is entirely based upon their patented fixed-seat iris design constructed with tempered stainless steel leaves attached to the iris body. All irises are built upon this superior principle and all additional features connected to and within iris combinations benefit from it. As a result of the Gehmann patent, the peephole seen by the shooter is absolutely circular throughout the full range of adjustments. Additionally, Gehmann irises can be cleaned with pressure air without risk of damage. All internal and external black surfaces are manufactured to give absolutely minimal light reflection, which is another cause of sight picture loss. All the irises are laser engraved. The reason the iris is so important to the shooter is it enables the shooter to achieve an extended depth of optical field necessary to clearly see both the foresight and the target picture at the same time.