XS Sights XTIs (Xpress Threat Interdiction Sight) for the AR-15/M16 are a secondary sighting solution that provide pistol sights on the side of your carbine that are designed for quick acquisition in CQB situations. Excellent addition to a 3-gun rifle when using magnified optics as the primary sight. Simply roll the rifle up your cheek to align the 45 degree angled sights. The lightweight design does not add unnecessary bulk or significant weight and the sights are reversible for left hand shooters.