From Enbloc Press:

The new rule will change how the legality of brace-equipped firearms is decided. The change will go into effect as soon as 08F is entered into the federal register, and, once law, affected gun owners will have 120 days to register their newly reclassified brace-equipped weapons as short barreled rifles (SBRs) or to modify, surrender, or destroy their firearms (lol. lmao, even).