ETF'sDO charge management fees--comparable to index mutual funds and almost as cheap as TSP funds.

I use a combination of ETF's and TSP funds to achieve a low cost, tax efficient, indexed portfolio.

I hold as much equity as possible in taxable accounts and hold taxable fixed income investments and tax-inefficientreal estate, dividend and microcap ETF's in tax deferred accounts.

And of course you have to invest in TSP for matching funds andfree dollar cost averaging and rebalancing.