This is a Magpul Industries Accessory known as the M-LOK Aluminum Rail, model MAG583.
Designed for use with all M-LOK compatible Hand Guards and Forends" M-LOK Aluminum Rail Sections allow the attachment of various 1913 Picatinny spec rail-mounted accessories such as lights" vertical grips" etc. Machined from milspec-anodized aluminum" M-LOK Rail Sections also feature beveled ends to reduce snagging and eliminate sharp corners and edges. All hardware necessary for attachment directly to M-LOK Slots on either aluminum or polymer hand guards and forends is included. 9 Slots" max overall length of 4.1". Made in U.S.A.
Features:
Directly mounts to M-LOK compatible T-nuts
Recoil/Impact mitigation lugs
Milspec-anodized aluminum
