At first glance, it looks like a simple piece of plastic or metal: a small, often red, oddly shaped fob meant to dangle from your keyring. However, to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and federal prosecutors across the United States, this "keychain" is considered a .
To understand the keychain, you first have to understand the part it mimics. A Drop-In Auto Sear (DIAS)
