Get it here… http://amzn.to/1XBnZ3o
Offset backup iron sights are designed to allow the user to quickly transition from a magnified optic to iron sights for close range shooting (or BUIS) without the need to break your cheek weld or move your hands off the rifle.
When mounted to a picatinny rail the BUIS are positioned roughly 45 degrees off center, which allows you to bring the sights into alignment by simply canting your rifle slightly to the side. This unique set up allows for lightning fast transitions between long & close range targets without the need to mess with your primary optics settings.