No exact language from a bill yet but here's the announcement: "Reps. DeGette and McCarthy Introduce Bill to Ban High-Capacity Assault Magazines."
The High Capacity Ammunition Feeding Device Act, as the bill is formally known, bans the sale or transfer of ammunition magazines holding more than 10 rounds. Such a standard was federal law between 1994 and 2004, when the assault weapons ban was in effect, and it is state law in many parts of the United States.
Note that it goes further than the AWB of '94 by banning the "sale or transfer" of existing magazines. Good luck enforcing that one, collectivist bitches. (Commentary on same found at Monderno.)