On April 5, 2011, FINRA and national securities exchanges filed a proposed plan with the SEC to establish a new "limit up-limit down" mechanism to address extraordinary market volatility in U.S. equity markets. The proposed mechanism would limit trades in listed equity securities to a price band set at a percentage level above and below the average price of the security over the preceding five-minute period, subject to certain exceptions. If approved, this mechanism would replace the circuit breakers which were put in place in response to market events on May 6, 2010. Comments must be submitted within 21 days from the date of publication in the Federal Register.  SEC Release. Proposed Plan.