This Retail Market Guide Revision Request (RMGRR) provides clarifications to Mass Transition processes and communications. The required minimum timeline for initial notification of a Mass Transition to affected parties is shortened from two hours to one hour, which in many cases will reduce the required Mass Transition timeline by a day. In addition, the RMGRR specifies that ERCOT may, if feasible, provide preliminary notification of a potential Mass Transition on a given Business Day to potentially affected Transmission and/or Distribution Service Providers (TDSPs), Providers of Last Resort (POLRs), and Public Utility Commission of Texas (PUCT) Staff, as long as Protected Information is not disclosed. This would allow affected TDSPs, POLRs and PUCT Staff to be adequately prepared should a Mass Transition event occur that day. This RMGRR also clarifies that ERCOT may coordinate periodic testing of Mass Transition systems and processes with Market Particpants.