Back Up Iron Sight - When optics fail the sight can easily be flipped up for an immediate sight picture. Clean streamlined appearance, simple function, and smooth integration with upper receiver. No small or fragile components to fail. Utilizes standard A1 hardware for serviceability. Cannot be accidentally adjusted out of position. Extends 3.250" over barrel and clears M4 handguards to provide room to forward mount reflex optics or mount scopes and maintain the proper eye relief. Elevates to 1/2 inch and has a smooth low profile interface.