SIFMA provides comments to the Securities and Exchange Commission (SEC) on the SEC’s order instituting proceedings to determine whether to disapprove self-regulatory organizations (SRO) proposed rule changes relating to trading halts due to extraordinary market volatility and requesting additional comment.  The relevant SRO rule filings are: File Numbers SR-BATS-2011-038; SR-BYX-2011-025; SR-BX-2011-068; SR-CBOE-2011-087; SR-C2-2011-024; SR-CHX-2011-30; SR-EDGA-2011-31; SR-EDGX-2011-30; SR-FINRA-2011-054; SR-ISE-2011-61; SR-NASDAQ-2011-131; SR-NSX-2011-11; SR-NYSE-2011-48; SR-NYSEAmex-2011-73; SR-NYSEArca-2011-68; SR-Phlx-2011-129.  SIFMA has long advocated for the adjustment of the current market-wide circuit breakers and provides in this letter additional comments on ways in which to modernize them.