These have to be registered don't they

http://www.botach.com/products/caa-roni-g2-9-glock-pistol-to-carbine-conversion-stock.html

Fixed your link

http://www.botach.com/products/caa-roni-g2-9-glock-pistol-to-carbine-conversion-stock.html

I do believe that these would have to be registered as a SBR as you are creating a firearm that is designed to be fired from the shoulder, with a rifled barrel that is less than 16 inches

http://www.botach.com/products/caa-roni-g2-9-glock-pistol-to-carbine-conversion-stock.html

thanks, that's what I though.

Definitely needs a stamp. And pretty damn irresponsible of Botach to not tell their customers. I wonder how many unknowing people have purchased these and are now in possession or an illegal SBR ?

Why the mandatory rail?



Features

No pistol disassembly required -just "drop" it into the shell.
It is mandatory that the pistol has the integrated below rail.
24cm upper flattop rail - allows combinations of sight, magnifier or night vision.
Three Picatinny rails for additional accessories.
Optional to add flip-up Backup sights (#FRS / #FFS).
Accepts silencers - up to 35.5mm diameter.
Optional to add quick release brass-catcher.
Including Detachable folding forearm grip, rear spare magazine holder & a safety-catch for the trigger's guard.
The Roni-G2 fits several types of Glocks (17, 18, 19, 22, 23, 31, 32).

I assume that is how the stock attaches to the pistol.

Yes, the body of the stock attaches to the rail on the pistol