The amazingly versatile M4S1 carbine handguard with interlocking top and bottom handguard sections offers multiple mounting options to your M16 or AR-15. Includes 2 mounting points with push-button quick-detach sling swivel. Bottom rail that can be mounted to the existing sling swivel mount for additional rigidity. Lightweight polymer handguard with heat shields is specially designed to withstand the extreme operating temperatures of a gas piston system. Upper and lower handguard sections interlock to offer the rigidity and stability you need in addition to solidly mounting to the delta ring and handguard end cap. An interchangeable 4" and 1.75" bottom rail allow you to quickly change rails based on mission need. Two 1.75" side rails give you mounting options for lights and lasers while providing a comfortable area to grip the handguard. Lifetime warranty.