The Trijicon MRO Mount uses the BLACR (Bobro Lever Auto Compensation, Reduced) system. The BLACR is a smaller version of the proven BLAC mechanism. We used the more compact BLACR because the MRO optic body is compact, and the BLACR system goes well with this configuration.
The base is the same height as the factory "low", and mounts the optic as low as possible. Applications include shotguns and AK pattern weapons etc.
The Co-witness riser puts the optic at 1.465" This will put the MRO at the same height as the iron sights on the M16/AR15 family.
The Lower 1/3 puts the optic at 1.765" This has the MRO running a little higher.
Because the system is modular, you can configure any of these heights, at any time. If you just have the base unit, and then want to change the height, then just order a riser. We provide all the tools and screws needed.