This is a Midwest Industries Handguard known as the Drop-In, model MI-17M.
Midwest Industries MI AR-15/M16 M-Series Carbine Length M-Lok Two Piece Drop-In Handguard is incredibly lightweight. It installs in minutes like factory handguards and has five anti rotation QD socket locations for QD swivel rings. It has a monolithic type continuous Mil-Std 1913 top rail.
Features:
Compatible with some gas piston systems
Lifetime warranty
100% Made in the U.S.A