On November 8, the SEC approved new rules to strengthen the minimum quoting standards for market makers and effectively prohibit “stub quotes” in the U.S. equity markets.  Executions against stub quotes represented many of the trades executed at extreme prices on May 6 and subsequently broken.  The rules require market makers in exchange-listed equities to maintain continuous two-sided quotations during regular market hours that are within a certain percentage band of the national best bid and offer.  The requirements become effective on December 6. SEC Release. SEC Rule.