Description Our Quantum Series M-LOK Handguards minimize bulk while providing an adaptive free float design that is big on features. With multiple mounting options, this affordable, rigid system can adapt to any mission. Machined to exacting dimensions from 6061-T6 aluminum it is the perfect handguard for your next AR15 build. Features: Designed to work with our M4E1 Upper Receiver 1pc free float design Removable 4-slot picatinny rail section for front sight Built in anti-rotation tabs 8 mounting surfaces for M-LOK accessories 1.78" inside diameter fits most muzzle devices and 1.5" suppressors Compatible with low profile gas blocks Made in the USA Are you attaching this handguard to a standard threaded upper receiver? Make sure to select "Yes" under the BAR Barrel Nut option above (shims included). Our handguards use the BAR interface and do not work with a standard barrel nut. If you are using our M4E1 Enhanced Upper Receiver, no additional pieces are needed. *Please note - This handguard is specific to the AR15/M4E1 platform. It is not compatible with the M5 .308/M5E1 platform. May not be compatible with all offset sights. *Polymer front Magpul MBUS sights may require modification to the sight for installation.