Knight's Armament Free Float Rifle RAS Mk 12 Mod 1 5.56 with Three 11-Rib Panels Black. The rail free floats the barrel allowing for consistent barrel harmonics upon firing and thus increased accuracy potential. Includes three KAC 11 Rib Rail Panels. Rifle Requirements: This Free Float RAS requires that the rifle have a carbine or mid length gas system and a low-profile gas block. Disassembly of the rifles gas system and removal of the factory barrel nut will be necessary. This forend uses a proprietary barrel nut that may be installed using a standard AR-15 armorers barrel nut wrench (sold separately). For AR-15/SR-15 based platforms only; not compatible with SR-25 variants. Specifications for Knight's Armament Free Float Rifle RAS Mk 12 Mod 1 with Three 11-Rib Panels: Manufacturer: Knight's Armament Color: Black Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Handguard Length: 12 in Gun Rail: Free Float Weight: 16.3 oz Condition: New Additional Features: Free Float Country of Origin: USA Attachment Type: Picatinny Package Contents: Knight's Armament Free Float Rifle RAS Mk 12 Mod 1 with Three 11-Rib Panels Installation instructions Knight's Armament 21318: Free Float Rifle RAS Mk 12 Mod 1 5.56 with Three 11-Rib Panels Black