Quote from rmorse:
Every firm that offers free ETF trading has restrictions:
Are there any restrictions on the commission-free ETF trades?
The commission-free trades on the 30 iShares ETFs must be done online at Fidelity.com, Active Trader Pro, Wealth-Lab Pro, or through Fidelity's wireless channels. Commission-free trades apply to all buy and sell transactions on eligible iShares ETFs. All iShares ETFs are not margin eligible for 30-days from settlement, similar to mutual funds. For margin customers, positions will automatically become margin eligible in their account after 30 days from settlement.