*As far as I know they are exclusive to "First Focal Plane" scopes
*Both the turret adjustments and distances are in Milradians(MRADS, MILs) like most modern tactical scopes.
*There are numerous variations H58,59, and 37 being the most common I have come across.
*If anybody has any questions please feel free to ask. I know a reasonable amount about shooting and optics.
*The main web sight is http://www.horusvision.com/
NOTE: on the "Horus Reticles" tab at the very bottom there's a simulator that show you how it works.