The BLACKHAWK folding front BUIS (back-up iron sight) is a folding front sight made to be compatible with standardized systems The sights work with Mil-Spec height rear AR sights, and use standard Mil-Spec front sight posts and sight adjustment tools Spring-deployed, the BLACKHAWK folding front iron sight folds out of the way when not needed, and its light weight won't affect the balance or handling of your gun