What are some good (
largest popular) instruments/ETFs to use when buying options on the S&P500 and DJIA?
By good I mean have very good liquidity, even when buying/selling further from the money, and hence ideally smaller spreads.
I don't know what is available for DJIA and only know of one, SPY, for S&P500. I haven't looked into this whole subject at all, so all answers/comments are appreciated. Thanks.