Not 100% sure on that I read a post not even 10 minutes ago that had the atf rules/guidelines that said if the brace and pistol are in the same area not attached it would still have to be stamped I’ll see if I can find that link I may have read it wrong.
Item Name: FS/FT NIB Multi Cal Stripped Lowers
Zip Code: 30529
Item is for: Sale or Trade
Sale Price: 300
Trade Value or Items Looking For: Surprise me.
Caliber: Multi Cal.
Willing to Ship: No
Bill of Sale Required?: No
Item Description: several lowers and other parts...