The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is issuing this open letter to further assist the firearms industry and the public in understanding whether a “partially complete, disassembled, or nonfunctional” receiver of an AR-15/M-16 variant weapon has reached a stage of manufacture such that it “may readily be completed, assembled, restored, or otherwise converted” to a functional receiver, and is therefore classified as a “frame or receiver” or “firearm” in accordance with the final rule titled “Definition of ‘Frame or Receiver’ and Identification of Firearms (Final Rule 2021R-05F), which became effective August 24, 2022.