The QF B.U.S (Back Up Sight) can be used as both a back up sighting system for rifle optics or as a primary sighting system

The sights must be manually flipped up and are secured using the sight’s internal tensioning feature

A2 front sight post can be adjusted for elevation. And the rear flip sight can also be adjusted for windage

This is a complete sight set

They are made of aluminum and can be mounted to your A3 upper receiver and a free float rail or high rise railed gas block. 

MADE IN THE USA AT STANDARD MANUFACTURING CO LLC