Clients of TD Ameritrade will now be able to trade 100 exchange traded funds commission-free.

The ETFs eligilble for commission-free trading include funds from Blackrock’s iShares and Vanguard.  Among the 100 eligible ETFs are the the iShares S&P 500 Index Fund (IVV) and the Vanguard Small Cap ETF (VB).

ETFs held for less than 30 days will be subject to a short-term trading fee.

See the TD Ameritrade ETF Center for more.