FN FN15 M4 5.56MM NATOMILITARY COLLECTOR SERIESRECEIVER-Hard anodized aluminum-Flat-top receiver, M-1913 MIL-STD rail at the 12 o'clock position-A2-style front sight, adjustable rear sight-UID labelBARREL-14.7" button-broached, chrome-lined-A2-style...