KNIGHT'S ARMAMENT PICATINNY RAIL RIB PANELS 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. SPECS Ribs: 2, Length: 1.65" Ribs: 4, Length: 2.65" Ribs: 5, Length: 3.47" Ribs: 6, Length: 3.90" Ribs: 9, Length: 5.48" Ribs: 11, Length: 6.15" Mfg: Nightforce