The "F" marked forged front sight base is a hard product to find. Mil-Spec for rifles issued to the troops require taller front sight bases on all flat top AR rifles. (.625") Designed to match the height of Mil-Spec height rear iron sights. These are new and are not yet drilled for taper pins, and should be installed by a qualified gunsmith. This includes front sight base only. (Not included are front sight post assembly, sling swivel assembly, and taper pins.)