Class 3 items are another name for NFA (National Firearms Act) items, like short barreled rifles/shotguns, machine guns, silencers, Any Other Weapons, destructive devices like grenades and rockets. How it relates to this ruling affects weapons that are currently classified as pistols (like Dracos, or rifle caliber pistols) that the ATF had previously told us we could put a brace on and it will still be a pistol. The new ruling is them changing their mind about the braces, and saying the brace makes that pistol an SBR (short barrel rifle) now. Having an unregistered SBR is a felony and is punishable by up to $10k or 10 years in prison.
The ATF is offering pistol brace users 120 days of anmesty to register their weapons and not have to pay the $200 tax normally imposed to have a class 3 item. People like myself who have paid thousands in $200 tax stamps alone, are intrigued by the idea of getting more tax stamps without paying $200 each time.