WHAT DOES FO FRONT MEAN?

† NOTE: The receiver-mounted, Picatinny-design and style rail is built to accommodate most optics and optic mounts supposed for use with Picatinny/ MIL-STD 1913 rails. Even so, resulting from decreased clearance concerning the top of your receiver and the bottom in the optics rail, optics and optic mounts that extend greater than .Ruger’s frict