Knights Armament (KAC)
KAC’s iconic Ribbed Rail Panels have seen use all over the globe on US military M4 Carbines. The lightweight polymer panels are ribbed for an enhanced grip, and help insulate the support hand from barrel heat. While originally designed for use on the KAC M4 RIS and M4 RAS rails, these panels are also compatible with many other railed handguards.
These are "new old stock" rail covers made after Knights moved from Vero Beach, but before 2009 or so, when the rails started to have CAGE Code numbers also attached. Some collectors would consider these slightly more desirable than CAGE Code marked, which are current production.
Typically, an 11-rib RAS rail cover - the largest - would fit the full length of an M4 Carbine RAS Quad Rail. The 9-rib might be wanted where the last part of a Picatinny rail is desired to be exposed, or with multiple rail covers on an M4 Rifle RAS Quad Rail, or even a Free Floating KAC Quad Rail found on the Mk12 Mod 1 rifle.
Charlie's also carries the military contract version of this rail cover: P&S - PAT mil-spec 9-rib rail panel