The term co-witness refers to the alignment of an accessory optic and the embedded sights of a firearm or non-electronic backup sights. Both the optic and sights result in the same point of impact and can be used as an alternative should the optic malfunction (e.g., a dead battery). In most cases, shooters prefer to co-witness their red dot optic and the sights manufactured into the slide of a handgun or to the rear and front sight post of an AR-15-style rifle. There are two types of co-witness: absolute or 1/3 (lower third). Absolute co-witness describes when the center of the optic reticle aligns with the center of the front sight (or top). 1/3 refers to the center of the iron being in the bottom 1/3rd of the optic viewing window but still retaining the same zero. The advantage of doing this includes the ability to accurately engage a target through the optic in the event of a malfunction. It is particularly important for handgun buyers who intend to mount a red dot optic on their firearm to ensure their analog sights co-witness to their red dot.