Barry Dueck, head of SureFire’s Suppressor program, nationally ranked 3-Gun competition shooter and former Marine developed the Rapid Transition Sight for the competitive or combat shooter who prefers separate sighting systems for near and far targets. With a goal of not adding weight he settled on the M4 sights, engineering them to mount to the upper Picatinny rail but at an offset of 45° to avoid conflicting with the primary sight. 
Since most everyone already carries a Back Up Iron Sight of one form or another as well as relies on the standard M4-style Front Sight, the RTS adds no new weight and essentially offsets these items to be more effective for close in targets when rifle mounts a telescopic sight for those mid and long distance shots. Many shooters are also very comfortable with the issue M4 sights so there is no issue associated with learning a new system and the you don’t have to deal with co-witnessing sights.
Tags: Barry Dueck, Dueck Defense