AIM ASI-MT021 Metal Carbine-Length AR-15 Quad-Rail Handguard System Amazon offers the AIM Sports Solid Metal Carbine Length Weaver / Picatinny Quad Rail Handguard System shipped FREE from the The Global Sportsman. Comes with two alloy handguard halves and Allen head screws. This is a carbine-length AR-15/M-4 quad-rail system, so it will be too short for …