Your M4E1 upper receiver isn't complete without the Aero Precision AR15 Quantum M-LOK Handguard. When you upgrade your rifle with these AR Handguards & Forends by Aero Precision, you gain 8 mounting surfaces for M-LOK accessories. That means more room for your customization needs such as lasers, optics or weapon lights. Another great feature of the AR 15 Quantum Free Float Handguard is that it boosts accuracy when resting the rifle on an unconventional surface. The handguard eliminates any direct point of contact between the barrel and the surface it's resting on, making your shots much more precise. Plus, this product provides better cooling for your barrel, which is especially useful if you have a long session at the range. You'll love the advantages of enhancing your firearm with the Aero Precision Tactical AR15 M-LOK Handguard. Please note that this handguard is specific to the AR15/M4E1 platform and IS NOT compatible with the M5 .308/M5E1 platform. Also, polymer front Magpul MBUS sights may require modification to install this product. If you are attaching this handguard to a standard threaded upper receiver, then you will need to purchase a barrel nut that is not included with this item. However, if you're using an Aero Precision M4E1 enhanced upper receiver, then no additional parts are needed.