From the manufacturer:
Rapid target acquisition is a critical component of defensive shooting. Designed by two highly experienced U.S. Special Forces veterans, the R4E Optimized Duty Sights have FIVE elements for sight alignment.
Three vertical features and two horizontal lines which produces a reticle type sight picture that improves target acquisition time.
Tritium enhanced lines on the rear sight help improve target acquisition in low light conditions.
This design provides the ability to swiftly line up your sights up on the target, which is vital to any shooter, especially to law enforcement and defensive shooters.