With a reputation that proceeds itself the Knights Armament RAS handguard line is well known for its rugged and dependable free float design. Specification unique to each handguard are as follows: 100-027-604 PN 20211 Dubbed the 'Too Long' this handguard is 13/16" longer than the carbine length handguard and requires the use of a low-profile gas block Approximate length: 7.61" Approximate weight: 1.06lbs 100-027-606 PN 21166-2 Dubbed the RAS MRE (More Real Estate) this is design for a carbine length gas system with a fixed front sight Approximate length: 11.27" Approximate weight: 1.26lbs Mfg: Knights Armament