This is the complete pin set for the Springfield Armory Echelon Variable Interface System. The Variable Inface System employs patent-pending self-locking pins to complete the most advanced optics mounting system on the market. As the mounting screws are torqued to spec, the pins exert lateral pressure on the optic's interior mounting surface to eliminate variance and left/right movement. The result is an unparalleled fit between the slide and a wide variety of optics. Includes Pin Set 1, Pin Set 2 and Pin Set 3.The Variable Interface System allows users to mount over 30 optics directly to the slide without the use of adapter plates. Simply configure the self-locking pins for the footprint of your desired optic to achieve a low, direct mount for improved sight picture and intuitive alignment. CompatibilityPin set 1 is compatible with optics that share the Trijicon RMR footprint.Pin set 2 is compatible with optics that share the Leupold DeltaPoint Pro footprint. Pin set 3 is compatibl...