Knight's Armament SR-16 CQB 11.5 inch upper receiver. These were originally sold to the US government, then bought back as over runs. They have gone through US government acceptance testing of 125 rounds fired. They are now marked "Commercial" on the underside of the receiver to show that they are buybacks. These are very rare, government production complete uppers. Comes with BCG, charging handle, and iron sights, ready to install on your SBR or pistol lower.
Determined at checkout.