This is a Magpul Industries Handguard known as the X-22 Backpacker Forend, model MAG1066-FDE.
The X-22 Backpacker Forend is intended for use with additional barrels for rifles currently equipped with the X-22 Backpacker Stock" MAG808. Its minimalist design offers a convenient package without compromising shooting performance. It is compatible with factory and aftermarket barrels up to 0.92" outer diameter. Constructed of a durable advanced polymer" the X-22 Backpacker Forend features a unique locking interface to attach the barrel assembly to the stock body when being transported.
Features:
Reinforced polymer construction for strength and durability
Compatible with factory and aftermarket barrels, up to 0.92Â OD;Ergonomic hand guard;Unique locking interface to attach the barrel assembly to the stock body when being transported