WHAT DOES 3RD ONLINE MEAN?

† Take note: The receiver-mounted, Picatinny-model rail is made to support most optics and optic mounts meant for use with Picatinny/ MIL-STD 1913 rails. Having said that, resulting from lessened clearance in between the best with the receiver and The underside on the optics rail, optics and optic mounts that stretch in excess of .Patent pending