The Ultradyne C4 Flip-Up Rear Sight utilizes Ultradyne's exclusive dynalign sight picture technology for accurate and immediate acquisition. Most BUIS systems utilize a sight picture that is non-intuitive. In such systems, the brain's visual systems are asked to align a circular rear aperture with a rectangular front post shape while simultaneously ignoring the 'ears' that protect the front sight post. Dynalign's circle-within-circle sight picture allows for faster sight picture acquisition. Additionally, the use of a front aperture further reduces parallax effect which makes accuracy less depend on precise sight alignment. Dynalign is a faster and more accurate sight picture than can improve shooting performance. FeaturesPurely Concentric Sight PictureMaximum FlexibilitySuperior Side-Adjust ErgonomicsOne-Handed Deployment and StowageInterchangeable ApertureMIL-STD-1913 Picatinny RailIncludes .070" Aperture CNC Machined